This invention relates generally to ball mill grinding assemblies, and particularly to ball mill grinding assemblies including an automatic ball charging and indexing device.
In general, a ball mill is configured as a cylindrical device, and is utilized for grinding crushed materials. Ball mills are widely used in production lines for powders such as cement, silicates, refractory material, fertilizer, glass ceramics, and the like. Ball mills are also used for ore dressing of both ferrous and non-ferrous metals. A ball mill is capable of grinding various ores and other materials either wet or dry. There are many types of grinding media suitable for use in a ball mill, each material having its own specific properties and advantages. Key properties of grinding media are size, density, hardness, and composition.
Ball mills rotate around a horizontal axis, partially filled with the material to be ground plus the grinding medium. Different materials are used as media, including ceramic balls, flint pebbles and steel balls. An internal cascading effect reduces the material to a fine powder. Industrial ball mills can operate continuously, fed at one end and discharged at the other end. Large to medium-sized ball mills are mechanically rotated on their axis, but small ones normally consist of a cylindrical capped container that sits on two drive shafts (pulleys and belts are used to transmit rotary motion). High-quality ball mills are potentially expensive and can grind mixture particles to as small as 5 nm, enormously increasing surface area and reaction rates.
During the ball milling operation, the grinding media, e.g. the steel balls, wear down and need to be replenished. This has typically been a manual operation, which is both tedious and dangerous. Grinding balls need to be added often in order to maintain optimum grinding characteristics. Steel balls, for example, may need to be replenished at a rate of about 100 barrels per month. Each barrel weighs approximately 2,000 pounds, and the balls must be added to the system in a controlled fashion. This is generally a two-person operation. The task is further complicated by the fact that natural weathering causes bridging and agglomeration of the balls, which further heightens the danger and difficulty of controlled stepwise addition of the grinding media to the system.
The present inventors have developed an assembly for automatically feeding grinding media to a ball mill assembly which mitigates the danger and provides an assembly of elements for receipt of grinding media and controlled addition to one or more ball mill grinders, so as to insure that optimal grinding parameters are maintained.
U.S. Pat. No. 5,224,659 to Gabardi discloses an apparatus for feeding balls to a grinding mill. The apparatus includes a downwardly inclined chute adapted to receive balls from a bin or hopper, and for delivering the balls to the grinding mill. Means for sequentially feeding the balls, one-at-a-time, to the grinding mill are provided, including a first actuator and a second actuator. Each of the actuators preferably includes an extension arm mounted for rotation along the longitudinal axis of the chute. The first actuator is for restraining balls from traveling down the chute and works in conjunction with the second actuator for isolating the lowermost ball in the chute to be fed next to the grinding mill. The second actuator is for releasing the isolated ball. The feeding means may include a computer controller for operating each of the actuators at a predetermined time interval corresponding to the ball attrition rate of the grinding mill. A magnetic sensor may be positioned inside the chute downstream from the actuators for sensing passage of the isolated ball through the chute for providing feedback to the controller.
U.S. Pat. No. 4,643,365 to McKim discloses an apparatus for adding grinding media to a grinding mill. The apparatus comprises a supporting structure including a face plate adapted to be mounted on a wall of a hopper or pipe containing the grinding media, a resilient rubber wheel mounted on the supporting structure and protruding through a slot in the face plate and said wall of the media container, and means for rotating said wheel at a low speed for withdrawing grinding media from said container and delivering the same to other conveyances for direction to the grinding mill.
U.S. Pat. No. 4,715,546 to Holming et al. discloses an apparatus for uniformly feeding grinding balls to a grinding mill. The apparatus includes a ball storage hopper, a regulator and an inclined chute for conveying balls from the hopper to the regulator. The chute includes a panel for controlling the depth of the balls. The regulator includes a discharge drum having a plurality of compartments adapted to receive the balls, an electric motor for rotating the drum, and a means for retaining the balls in the drum. The drum is rotated at a predetermined speed and feeds the balls into a mill at a uniform rate, which can be controlled to approximately match the attrition rate of the balls in the mill.
U.S. Pat. No. 3,773,268 to Bond discloses an apparatus for and a method of controlling the feed rate of grinding media to a grinding mill of the type that operates at a power draft in the vicinity of the critical peak power draft of the grinding mill. In the described embodiment, the ore grinding media feed rate to a secondary autogenous grinding mill is controlled. In the described embodiment the ore grinding media feed rate is normally automatically controlled in response to the electrical power demand of the grinding mill by control means whose function is to maintain the power draft of the mill at a predetermined set point. At suitable time intervals, such as once every sixty minutes, the normal automatic feed control for the ore grinding media is interrupted or deactivated and an override feed control for the ore grinding media is substituted in place of the normal feed control. The override feed control acts to substantially decrease the rate of feed of the ore grinding media to the mill sufficiently to cause a measurable effect on the power draft of the mill. During the period when the override control is in effect, the feed of ore grinding media to the mill may even be stopped completely. A sensing device responsive to power increase or decrease detects whether the power input to the mill decreases or increases when the override feed control is in control, thereby indicating whether the mill is loaded below or above the grinding media charge or loading corresponding to the critical peak power draft of the mill. If the sensing device detects a decrease in power input to the mill during the override period, the override ore grinding media feed control is disconnected or otherwise deactivated and the normal ore grinding media feed control is reconnected or otherwise reactivated. If the sensing device detects an increase in power input to the mill during the override period, the override feed control remains connected to provide a decreased rate of feed of ore grinding media, which may even include a complete stoppage of feed of ore grinding media, until the sensing device detects a decrease in power input to the mill, at which time the override ore grinding media feed control is disconnected and the normal ore grinding media feed control is reconnected.
The references fail to teach or suggest a unitary ball feeding and indexing device, that serves the function of deagglomerating and directly distributing a plurality of grinding media (steel/iron balls) to a ball mill grinding system. The references further fail to teach a system whereby the grinding media are automatically indexed, separated from detritus and agitated to prevent agglomeration and bridging, which would otherwise prevent the flow of balls to the indexer wheel, as instantly disclosed.
Ball mills typically are loaded with iron, steel or ceramic balls, or combinations thereof, about the size of a baseball. The balls rotate within the housing of the mill, macerating/pulverizing the contents to a desired particle size. During this process the balls gradually wear down in size, and must be replaced on a continual basis in order to maintain efficiency. Heretofore feeding of the balls has been a manual job, which is both difficult and dangerous.
The present invention illustrates an auto-feeder system for a ball mill operation. The main component, as illustrated, is a ball indexer which permits balls (in bulk) to be filled into a hopper where they are agitated in order to deagglomerate them, and then the balls are metered out via the ball indexer, through a perforated chute (which allows for the jettisoning of extraneous materials) to a ball feed elevator, toward a diverter gate assembly (when multiple ball mills reside within the system), and ultimately to the ball mills themselves.
Other objects and advantages of this invention will become apparent from the following description taken in conjunction with any accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. Any drawings contained herein constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.
The invention is directed toward a material handling, processing and milling facility which utilizes ball milling as a means for material grinding, mixing or mechanical alloying of materials such as ores, chemicals, ceramic raw materials and paints.
With reference to
Referring now to
With further reference to
As further illustrated in
Referring now to
Referring more particularly to
In order to better understand the operation of the ball indexer assembly 200, an exploded view is shown in
The ball indexer assembly 200 is designed to perform a dual function. It receives grinding balls 606 from a bulk source, e.g. front end loader 200, a railroad car, dump truck or the like. The balls 606, first impact the rotating conical agitator 202 to prevent agglomeration and bridging, which would prevent the flow of balls 606 from reaching the slotted indexer wheel 210, which is illustrated as containing four slots 240, albeit this is a non-limiting configuration. Continual rotation of the now deagglomerated balls 606 allows them to fall into (4) four grinding ball receiving slots 240 in the slotted indexer wheel 210 located in the periphery thereof. The balls 606 then fall through the window insert 214. The window insert 214 is a replaceable wear item, which can also be changed to allow for different sized balls. The speed of the gearmotor 208 is adjusted such that the balls 606 are fed at the desired controlled feed rate and the proper trajectory through the window insert 214. In order to insure centering of the balls 606 in the window insert 214 a centering block 212 is provided. This piece is also a replaceable wear item that can be changed to accommodate different sized balls.
Rotation of the agitator 202 and indexer wheel 210 is effectuated via the gearmotor 208. Gearmotor 208 is bolted to hopper bottom 232. The torque of the gearmotor shaft 242 is transmitted through bearing shaft 218, which is bolted to the slotted indexer wheel 210.
The gearmotor shaft 242 is connected to bearing shaft 218 via output shaft 228. The rotational, thrust and axial forces are transmitted through bearing 220, which is retained by bearing collar 216 on the outer race and bearing shaft 218 on the inner race. The bearing 220 is protected from dirt and water intrusion by bearing seal 222. Grease is retained in the bearing 220 by bearing seal 222 and inner bearing seal 230. The bearing is supplied with lubrication grease through grease fitting 234, which is installed in tapped holes in the hopper bottom 232.
All patents and publications mentioned in this specification are indicative of the levels of those skilled in the art to which the invention pertains.
All patents and publications are herein incorporated by reference to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference.
It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification and any drawings/figures included herein.
One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objectives and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiments, methods, procedures and techniques described herein are presently representative of the preferred embodiments, are intended to be exemplary and are not intended as limitations on the scope. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention and are defined by the scope of the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention, which are obvious to those skilled in the art, are intended to be within the scope of the following claims.
This application claims benefit of priority to U.S. Provisional Patent Application Ser. No. 61/752,696, filed on Jan. 15, 2013, the contents of which are herein incorporated by reference in its entirety.
Number | Date | Country | |
---|---|---|---|
61752696 | Jan 2013 | US |