Patent Publication Number: US-3876160-A

Title: Centrifugal ball mill

Description:
United States Patent Bloch Apr. 8, 1975 [54] CENTRIFUGAL BALL MILL 3.524.735 8/1970 Oetiker 24l/l75 X 79.920 5 l97l H 4 X [76] Inventor: Rudolf Moshe Bloch, 11 3 5 2 fi f&#39; Beer shew Primary ExaminerRoy Lake Srae Assistant ExaminerE. F. Desmond [22] Filed: Aug. 6, 1973 Attorney, Agent, or FirmHubbell, Cohen, and Stiefel [2|] Appl. No: 386,063 [57) ABSTRACT I A centrifugal ball mill wherein means are provided for gn ppl P r y Data actuating the planetary rotational movement and sepa- Aug. 8, 1972 Israel 40067 rate means for actuating the rotational movement of the mill barrel about its axis of rotation. The axis of [52] U.S. Cl. 241/175 h lling vessel n e parall l i h he axis of the {51] Int. Cl. B02c 17/03 rotation of h pl n ry movement or perpendicular [58] Field of Search 24l/l75-177 thereto. When the axis of rotation of the milling vessel is in a plane perpendicular to that of the axis of rota- [56] References Cited tion of the planetary movement, the angle of the axis UNITED STATES PATENTS of the milling vessel can be varied respective the ra- 2,8l0 l56 10/1957 Long 241 175 x of the mammary mmemem&#39; 2.937.8l4 5/l960 Joisel .4 241/175 7 Claims, 4 Drawing Figures 17 I l X 14 t2 1 l X 15 PATENTEBAPR ems 7 876, 160  
 sezzar 2 Bf 2 FIGURE 3 FIGURE CENTRIFUGAL BALL MILL BACKGROUND OF THE PRESENT INVENTION Conventional ball mills are widely used in laboratories and in industry. They are used for grinding and for mixing various materials. and this is accomplished by inserting the material to be ground. together with balls of another. hard material into a substantially cylindrical vessel which is revolved about its axis at a predetermined speed of rotation. The material is ground by the action of the accelerating forces of the balls. When gravitational forces are used. the effect is the better. the larger the diameter of the cylindrical vessel. The velocity of rotation can be varied only within certain limits. as for each material and diameter there exists 2! limiting value of the rate of rotation beyond which the balls remain stationary on the wall of the vessel. turn with same and do not effect any grinding.  
  An improvement of the simple ball mill comprises a ball mill arranged planet-like on or close to the circumference of a turning wheel. In such a ball-mill centrifugal forces are used. and a substantial improvement in performance of the mill can be achieved. The planetary movement is actuated by means oftransmission belts or piston arrangements. A ball-mill of this type has been described by R. Bloch and C. Rosetti in Chemiker Zeitung I932 page I96. Due to the utilization ofcentrifugal forces. good grinding effects could be obtained in a vessel ofa volume ofonly 300 ml and the ground material could be recovered practically without any losses. One motor was used for actuating the planetary movement and for the rotation of the cylindrical millingvessel around its axis. Thus these are interconnected and cannot be varied at will independently of each other.  
 DESCRIPTION OF THE PRESENT INVENTION According to the present invention there is provided an improved centrifugal ball-mill which is characterized in that individual means of actuation are used for rotating the circular support member on which the milling vessel or vessels are arranged. and for the actuation of the rotational movement of these around their own axis. Thus any desired rotational velocity of the rotating circular support member and of the rotating miliing-vessel or vessels can be obtained. This makes it possible to use optimal combinations of rotational velocities. according to the nature of the material to be ground. and to the material of the balls used for the grinding. The independent regulation of the rotational velocities results in a substantial improvement of grinding efficiencies. According to a further embodiment of the invention, when the axis of the milling vessel is perpendicular to the axis of the rotating circular support member. means are provided for adjusting at will the angle of the axis of the milling vessel respective the ra dius of the circular support member. This results in further improvements of the performance of the ball-mill.  
  The present invention is illustrated by way of example only with reference to the enclosed schematical drawings, in which:  
  FIG. 1 is a side-view in partial section of a ball-mill according to the invention;  
 FIG. 2 is a top view of the ball-mill of FIG. 1;  
  FIG. 3 is a side-view in partial section of another embodiment according to the invention;  
 FIG. 4 is a top view of the ball-mill of FIG. 3.  
  As these embodiments comprise simple mechanical elements. in combination with conventional and wellknown means of actuation of the rotational movements. these are set out in a schematical manner and these need not be described in detail.  
  The ball-mill illustrated in FIGS. 1 and 2 comprises two milling-vessels 11, mounted not far from the circumference of the circular. wheel-like support member 12, which is attached to the slewing-ring l3, actuated by the motor 14 which actuates the slewing ring drive gear 15. This arrangement makes it possible to rotate the circular support member 12 at any desired velocity of rotation. which is adjustable at will within certain limits. The axis of the milling-vessels II is parallel to the axis of rotation of the circular support member 12. These cylindrical milling vessels are rotatably mounted on the support member 12. and are arranged opposite each other. Both of these are rotated about their axis of rotation by means of the motor 16, and the millingbarrel chain-drive 17. The velocity of rotation of the milling-vessels 11 can be adjusted within certain limits by changing the rate of revolution of the motor 16. When the circular support member rotates in a clockwise direction it is advantageous to rotate the milling vessels in a counter-clockwise direction. and vice versa.  
  It is also possible to provide two individual motors. with means for adjusting the rotational velocity, for each of the two milling-vessels. The velocity and number of revolutions per minute of the circular support member and of the milling vessels can be varied at will by suitable gears or by varying the voltage supplied to the motor. as by a variable transformer. Other conventional means may be used for the same purpose.  
  As shown in FIG. 4, the position of the milling-vessel respective the turntable may be varied. In full lines there is illustrated one position. the axis of rotation of the milling vessel being substantially perpendicular to the radius of the turntable (circular support member). In dashed lines there is shown another position. in which this axis is at a certain angle with the radius. This angular position has certain advantages. as it makes possible the use of higher rates of revolution per unit time of the milling vessel without the balls attaining the critical velocity. Due to the angle, the balls do not cling to the wall of the milling vessel up to a certain velocity. which is higher than that when the first position is used.  
  As the components in the above described drawings are substantially identical. the same designations have been used in these.  
  Centrifugal ball-mills according to the present invention can be of any desired size. from small-scale laboratory models and up to very large ones for use in industry, for size-reduction of ores and the like.  
  A laboratory model was constructed, having milling vessels of about 300 ml volume. The model described was one of the type illustrated in FIGS. I and 2, and the distance of the axis of rotation of the milling vessel from the center of the circular support was l7 cm. Two grinding balls of l.5cm diameter were used. The ball mill was actuated at 300 r.p.m. of the planetary movement and of 300 rpm. of the milling vessels about their axis of rotation.  
  The starting material was rock-crystal of the following particle size:  
  2 l% residue on a 49 mesh/cm sieve; 72% residue on a 169 mesh/cm sieve; 7% residue on a 225 mesh/cm sieve.  
  After grinding for minutes at the above rotational velocities the following particle sizes were obtained: 0% residue on 49 meshlcm 0% residue on lb9 mesh/cm&#34;; 7% residue on 225 mesh/cm 33 residue on 1600 meshlcm 209? residue on 4900 mesh/cm&#34;; 40% passage through 4900 mesh/cm sieve.  
  When the rotational velocity of the milling vessel around its own axis was increased to 600 r.p.m.. the rate of revolutions of the planetary movement remaining at 300 r.p.m.. the grinding time could be reduced to 7 minutes. giving the same results as before According to the present invention it is possible to use rotational velocities of the milling vessels close to the critical velocity (at which the grinding balls cling to the walls). and this is accomplished by gradually varying the rate of revolutions of the milling vessels at a given rate of revolutions of the circular support member.  
 Similar experiments were carried out with the embodiments illustrated in FIGS. 3 and 4 (also with the embodiment where the milling vessel is at an angle. The independently variable rotational velocities of the support and of the milling vessels make it possible to ob tain considerably better results than when these are interdependent and cannot be varied at will. each by itself.  
  It is clear that the above is by way of illustration only and that many changes and variations in the nature and arrangement of the components can be resorted to without departing from the scope and spirit of the present invention.  
 I claim:  
  1. A centrifugal ball-mill comprising a housing; a turntable rotatably mounted in said housing for rotation about an axis of rotation; first motor means drivingly connected to said turntable for rotatably driving said turntable about said turntable axis of rotation; first and second spaced apart milling vessel mounting means supportably mounted on said turntable for simultaneous rotation therewith about said turntable axis of rotation. each of said milling vessel mounting means being radially spaced from said turntable axis of rotation along a radius of said turntable; first and second milling vessels rotatably mounted in said first and second milling vessel mounting means. respectively. for rotation about respective axes of rotation in a plane parallel to the plane of rotation of said turntable. said plane of rotation being normal to said turntable axis of rotation; and second motor means drivingly connected to said first and second milling vessels for rotatably driving said first and second milling vessels about said respective milling vessel axes of rotation. said second motor means being independent of said first motor means.  
  2. A centrifugal ball-mill in accordance with claim I wherein each of said first and second milling vessel respective axes of rotation is normal to said turntable radius.  
  3. A centrifugal ball-mill in accordance with claim 1 wherein each of said first and second milling vessel respective axes of rotation is at a predetermined acute angle with respect to said turntable radius.  
  4. A centrifugal ball-mill in accordance with claim 1 wherein said first and second milling vessels are mounted opposite each other along a diameter of said turntable on opposite sides of said turntable axis of rotation substantially equidistant therefrom. and on opposite sides of said diameter. said diameter comprising each of said radii.  
  5. A centrifugal ball-mill in accordance with claim 4 wherein each of said first and second milling vessel respective axes of rotation is normal to said turntable diameter.  
  6. A centrifugal ball-mill in accordance with claim 4 wherein each of said first and second milling vessel respective axes of rotation is at a predetermined acute angle with respect to said turntable diameter.  
  7. A centrifugal ball-mill in accordance with claim 1 wherein said first motor means is drivingly connected to said turntable by gearing means and said second motor means is drivingly connected to said first and second milling vessels by chain drive means.