US3392924A

US3392924A - Multichamber mill

Info

Publication number: US3392924A
Application number: US547398A
Authority: US
Inventors: Schmitz Hugo
Original assignee: Kloeckner Humboldt Deutz AG
Current assignee: Kloeckner Humboldt Deutz AG
Priority date: 1965-04-30
Filing date: 1966-05-02
Publication date: 1968-07-16
Anticipated expiration: 1985-07-16
Also published as: BE679712A; ES326042A1; FR1483040A; DK123630B; DE1227316B; AT282313B; GB1145067A; CH432992A

Description

July 16, 1968 H. SCHMITZ 3,392,924

MULTI CHAMBER MILL Filed May 2, 1966 2 Sheets-Sheet 1 H4 SCHMITZ July 16, 1968 MULTICHAMBER MILL 2 Sheets-Sheet i( Filed May 2, 1966 United States Patent O 3,392,924 MULTICHAMBER MILL Hugo Schmitz, Beckum, Westphalia, Germany, assignor to Klockner-Humboldt-Deutz Aktiengesellschaft, Cologne, Germany, a corporation of Germany Fiied May 2, 1966, Ser. No. 547,398 Claims priority, application Germany, Apr. 30, 1965, Sch 36,968 4 Claims. (Cl. 241-137) My invention relates to a multichamber mill of the tube type having a plurality of grinding chambers rigidly connected to one another and located around a common rotational axis, the peripheral walls of the mill having no openings.

It is known that particularly `during fine-grinding in tube or cyinder mills, the tumbling media, such as metal balls, become loaded with too great an amount of kinetic energy. The energy of the tumbling media not employed for comminuting the charge of working material is transformed into mechanically produced heat. In many decades of tube mill development history, there has been no lack of endeavor to transform, by specially subdividing the mill cylinder into a plurality of coaxially disposed grinding chambers, at least a portion of the excess energy in the downwardly turning grinding chamber to driving energy for rotating the mill.

A heretofore known embodiment of a multichamber mill has a mill cylinder which is divided radially into live chambers. The walls of each individual chamber consist of substantially a fifth of the peripheral wall of the mill and two substantially fiat plates disposed with respect to one another so as to define an acute angle. In this manner, therefore live grinding chambers asymmetrical in cross section are formed. In accordance with the asymmetry of the chamber walls with respect to the rotational axis of the mill, the displacement of the tumbling media is also non-uniform or unbalanced. Since the chamber walls are not rotationally symmetrical, it is impossible to have a uniform state of motion of the aggregate tumbling media. In the upwardly turning portion of the mill, the flat partition walls serve as raising shovels. The tumbling media pile up in front of these partition walls so that the preponderant portion of the quantity of tumbler media is at a standstill and no comminuting action or at least only very little is performed because there is substantially no relative motion of the tumbler media component particles with respect to one another or at best there is relative motion of only a very small portion of the tumbling media pellets in the chambers.

In the downwardly turning chamber of these known mills, the quantity of tumbling media is shifted from the flat partition, which serves as the supporting surface, to the rotationally symmetrical casing of the mill. During the instant in which the downward motion of the grinding chambers takes places, the potential energy of the tumbling media proper is transformed in part to kinetic energy for the comminuting operation, while the remaining potential energy inures to or is applied to the turning moment of the mill. This reclaimed energy for driving the mill opposes the reduced comminuting action 4during the upward motion of the grinding chamber so that the throughput performance or efficiency is reduced, and the yield of the specific output or eiciency is further nullified or cancelled in part.

The afore-described known multiple chamber mills have 3,392,924 Patented July 16, 1968 "ice radially extending rotary surfaces or planes which differ from those of the invention in the instant application. If one were to consider the conditions at the upper apex or crest of the surfaces, the tumbling media, in contrast to the invention of the instant application, would be unable to be thrown, as hereinafter noted, relatively far onto the other side of the grinding chamber, but rather would accumulate in the angle or corner between both radially extending surfaces so that displacement of the center of gravity of the mass of tumbling media to the other side could not occur or could only occur to a small degree. Furthermore, the approximately triangular form of the grinding chambers in the aforementioned known mills cause the tumbling media to accumulate at three locations during rotation of the mill, i.e. in the corners or angles thereof, so that an especially short free slope or embankment is produced on which the comminuting action in essence is carried out. Thus the comminuting efciency of these known mills is relatively small.

It is accordingly an object of my invention to provide multichamber mill which avoids the aforementioned disadvantages of the heretofore known devices and which will enhance the throughput yield or eiciency of the mill.

With the foregoing and other objects in view, I provide each of the grinding chambers, in accordance with my invention, with peripheral walls comprising a iirst section curved more than and a second section spaced from the center of gravity of the cross-sectional plane of the grinding chamber a distance less than the distance of the first-mentioned section from the center of gravity, and both sections are so disposed with respect to one another that the section closer to the gravity center is slipped under the charge or quantity of tumbling media when the grinding chambers are moved upwardly.

With the multichamber mill of the invention, the convex sections (unsteady or changing planes) located relatively close to the center of gravity effect a rotation of the tumbling media approaching the crest of the convex sections. This rotation leads to a simultaneous movement of all the particles in the tumbling media whereby a grinding effect is achieved not only at the sloping surface of the tumbling media but also in the entire quantity of tumbling media particles. In this manner, therefore, the grinding eifect is increased. Disregarding that situation in which rotation of the tumbling media occurs, the tumbling media lie in the form of a slope or embankment in the vicinity of the grinding chamber section which is curved more than 180 so that a slope is formed there just as for single-chamber mills and the same comminution effect as in singlechamber mills is achieved. Moreover, the supply of tumbling media particles is thrown onto the other side of the respective grinding chamber due to the sudden rotation thereof in the vicinity of the apex of the convex section so that the center of gravity is displaced in the same direction and the turning moment opposing the drive moment is therewith at least partly balanced or canceled. Furthermore, the tumbling energy of the supply of tumbling media acts in the direction of the rotary motion of the grinding chamber so that this energy, insofar as it does not produce comminuting action, is applied toward driving the mill.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in multichamber mill, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalence of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specic embodiments when read in connection with the accompanying drawings, in `which FIG. l is a longitudinal section of a multiple chamber mill constructed in accordance with my invention;

FIGS. 2 and 3 are cross-sectional views taken respectively along the lines II-II and III-III in FIG. 1; and

FIG. 4 is a cross-sectional view similar to that of FIG.

3 of another embodiment of a grinding mill constructed in accordance with the invention.

As shown in the figures, the multichamber mill constructed in accordance w-ith my invention is provided with four

grinding chambers

2a, 2b, 2c, 2d, for example, symmetrically disposed about the axis of rotation 1 of the mill.

Flanges

3a and 3b secure the grinding chamber to the

partition walls

4a and 4b which are'in turn respectively connected by the

cylindrical rings

5a and 5b with the

side walls

6a and 6b of the mill. Hollow throat-like trunnions or

journals

7a and 7b are located on the

end Walls

6a, 6b and are rotatably mounted in

bearings

8a and 8b. A gear rim 9 is anged onto the end wall 6a and, by means of meshing pinion 10, which is dri-ven by a non-illustrated drive means, rotates the mill about the axis 1.

The working material which is to be comminuted is conducted through the hopper 11 onto the interior of the hollow cone 12. From the latter, the working material slides into the space 13 defined by the end wall 6a, the partition 4a, and a conical ring 14 located intermediate to the end lwall 6a and the partition 4a. In the upwardly turning portion of the mill, the working material lirst slides against a guide plate 15 (FIG. 2), and is then conducted from the latter through the openings 16 into the grinding chambers. The comminuted material discharges from the grinding chambers through the openings 17 in i out resulting in any reduction in the throughput efficiency of the mill. For this purpose, a predominant portion of the chamber walls, in fact the section 21 (FIG. 3), is curved more than 180 and is advantageous-ly cylindrically formed so that nearly during the entire rotation, i.e. also in the upwardly moving grinding chamber, the tumbling media can roll on the walls with varying velocity just as for a cylindrical mill, so that in the structure according to the invention there is also relative velocity between the particles in the aggregate tumbling media. Thus, in the mill constructed in accordance with my invention, comminuting action is being carried out at all times in each grinding chamber, whereas in theraforementioned known grinding mills this occurs predominantly only in the downwardly moving grinding chambers. With the embodiment constructed in accordance with the invention, however, as shown in FIG. 3, a further effect is obtained which is based upon the fact that the grinding chamber walls adjacent the section 21, which is curved more than 180, has a second section 22 which is spaced from the center of gravity 23 of the cross-sectional plane of the grinding chamber a lesser distance than the first-mentioned section 21 is spaced therefrom. The second section 22 (which forms a spatially varying plane) is curved o`r arches into the interior of the grinding chamber and is so located that, during the rotation of the mill in the direction of the arrow 24 with the upward motion of the grinding chambers, the section 22 gradually slides under the quantity of tumbling media particles and places the particles in the vicinity of the apex or crest of the convex section 22. Consequently, a displacement of the static and dynamic centers of gravity of the quantity of tumbler media and rolling of the tumbling media over the wall section 22 then occur. In connection therewith, there is a displacement of a moment in favor of or toward the clockwise `rotating positive turning moment 24. The 'required mill driving power is thereby reduced. With the rolling of the quantity of tumbler media over the convex or arched Wall section 22, the entire quantity of tumbling media is set into motion in a short time, accompanied bysliding movements within the aggregate tumbling media and a maximum of collision contacts. The entire number of collision contacts per unit time is thereby greatly increased as compared to mills of heretofore-known construction. This simultaneously produces a considerable increase in the specific output of the mill constructed in accordance with the instant linvention. Furthermore, the tinrrbling energy of thevr-otated tumbler media components in the rotary direction of the mill produces a decrease in the driving energy necessary for rotating the mill.

A further advantage of the mill'constr'ucted in accordance with the invention is that the tumbling media particles are partly supported by the convex or arched wall section 22 during the upward movement of the grinding chambers whereby it is possible to drive the mill with less rotary speed than is necessary for the heretofore-known mills. Since the driving power is proportional to the rotary speed, it follows therefore that the driving power of the mill constructed in accordance with the invention must be smaller proportionately as the rotary speed is smaller.

The iigures of the drawing show only examples of preferred embodiments for constructing the mill in accordance with the inventive concept of the application. Variati-ons thereof are of course possible without in any way reducing the inventive concept and within the scope thereof. For example, in FIG. 4 instead of the arched or convex wall section 22, a llat wall section 22a in the form of a chord located in the cross section of the cylindrical chamber Zat-2d can be employed with similar results. Instead of the ground material outlet 19 at the periphery of the mill, an outlet device can be employed equally wherein the ground material discharges from the throatlike trunnion 7b, for example. Furthermore, instead of having only four grinding chambers, it is of course clearly understood that any desired number of chambers can be employed.

It is also believed to be self-evident that in the empty cross-sectional space about the rotary axis 1 of the mill, a screw conveyor can be provided by means of which either all or a portion of the ground material can be returned from one or more of the grinding chambers again to the mill :inlet end 11 so as to be re-ground.

I claim: v

1. Grinding mill comprising a plurality of rigidly connected grinding chambers adapted to contain a quantity of tumbling media and disposed about a common rotational axis, said chambers having respective closed peripheral walls each comprising a rst section curved more than and a second section located closer to the center of gravity -of the respective chamber, in a cross-sec- `tional plane thereof, than said trst section, said sections being disposed relative lto one another so that said second section rides under the quantity of tumbling media in the respective chamber when said chamber is being moved in an upward direction about said' comm-on rotational axrs.

2. Grinding mill according to claim. 1, wherein said first section is at least partly cylindrical in form.

3. Grinding mill according to claim 1, wherein said second section is convexly arched in the interior of the respective grinding chamber.

4. Grinding mill according to claim 1, wherein said second section forms a chord extending across a crosssectional plane of the interior of the respective grinding chamber.

References Cited UNITED STATES PATENTS Eggert 241-137 Gibson 241-137 X Eppers 241-137 Fries 241--137 X HARRISON L. HINSON, Primary Examiner.

Claims

1. GRINDING MILL COMPRISING A PLURALITY OF RIGIDLY CONNECTED GRINDING CHAMBERS ADAPTED TO CONTAIN A QUANTITY OF TUMBLING MEDIA AND DISPOSED ABOUT A COMMON ROTATIONAL AXIS, SAID CHAMBERS HAVING RESPECTIVE CLOSED PERIPHERAL WALLS EACH COMPRISING A FIRST SECTION CURVED MORE THAN 180* AND A SECOND SECTION LOCATED CLOSER TO THE CENTER OF GRAVITY OF THE RESPECTIVE CHAMBER, IN A CROSS-SECTIONAL PLANE THEREOF, THAN SAID FIRST SECTION, SAID SECTIONS BEING DISPOSED RELATIVE TO ONE ANOTHER SO THAT SAID SECOND SECTION RIDES UNDER THE QUANTITY OF TUMBLING MEDIA IN THE RESPECTIVE CHAMBER WHEN SAID CHAMBER IS BEING MOVED IN AN UPWARD DIRECTION ABOUT SAID COMMON ROTATIONAL AXIS.