Technical Field

The invention relates to balls and rod mills used for grinding industrial mine and minerals, mainly cement and metal ores.

The invention particularly relates to spiral geometry ball or bar grinding mill with reduced energy consumption by bringing mill structure from circular form to spiral form and thus making consumed energy more efficient.

State of Art

Today balls and rod mills are used for grinding industrial mine and minerals, mainly cement and metal ores. Ball and rod mills have wet, dry, autogenous, semi-autogenous, continuous feeding or fill, gear driven, neck driven or direct on-body engine winding adapted grinding methods. Inner parts of them have steel, rubber or ceramic lining.

Said ball mills are rotating tubes of cylinder shape comprising steel or ceramic balls therein. During rotation of mill, balls apply pressure onto inner wall rotating under effect of centrifugal force. Balls rotate together with mill wall and travel up inside mill by help of friction force created by the pressure. Weight of balls defeats centrifugal force effect at a certain point inside wall and balls fall inside mill. In other words, while mill rotate at a certain RPM, balls go up and fall down continuously. Since all of balls do not touch wall, many balls move within the pile of other balls contacting wall. The motion created by such pile of balls is called cascade. Material fed into mill for grinding is crushed inside the cascade, is subject to friction, pressure and in the end is chipped and ground. During rotation central weight of the cascade is at a certain distance from mill rotation axis and applies a tangential force onto rotation axis. The moment created by such force at a certain RPM determines power of mill and power consumption in a certain period of running. Components such as diameter of mill, number of balls therein, RPM, lining structure specify place of cascade and the moment applied by cascade onto mill. Type of the cascade movement determines nature of grinding work in the mill, mill performance.

Also said ball mills can be of continued type wherein material is continuously fed and ground material is continuously are given from the mill or batch type wherein discharged after completion of grinding. Said rod mills are the mills where steel bar form are used as grinding material instead of ball. Autogenous mills are the systems where only material grinds material inside the mill without grinding ball or rod. Semi-autogenous is the system where few amount of ball and remaining material perform grinding.

In addition, dry and wet terms are used for ball mills. For wet mills water is added with the material. Material is grinded in a full sludge medium with water and material in the mill. Wet grinding is conducted generally for metal ores. Cement and industrial minerals are also grinded in general by dry grinding. Rod mills are used with wet grinding.

Inside of ball mills is coated with steel, rubber or ceramic material durable against wearing in order to prevent drum wall wearing. Lifter bars are also placed in some parts of such coating to help raise of material. The lifter bars also help delay in wearing of coating where ball and material remain on coating for longer time periods.

In the prior art, power consumption of ball mills is high while their efficiencies are low. According to research conducted, power efficiency of ball mills is about 6 %. In other words, 6 % of supplied electric energy is consumed on grinding. The remaining is lost as heat, sound, mechanic efficiency, bearing frictions etc.

In the related art there are also other grinding machines with high energy efficiency alternative to ball mills. For instance, efficiency in vertical roller mills is about 8 % and in horror mills it is about 12 %. Although these machines have high energy efficiencies, initial investment, maintenance and other operating costs are high.

In the related art ball mills conduct crushing with balls falling from height at high speed inside cascade, wearing with those rolling and pressure force with slow motion at mid-points of cascade. In this context, grinding is conducted by mid part pressure force caused by too slow motion inside cascade. Since this part moves too slow and even hardly move, and thus creates weight at a point far from centre inside the mill, it creates moment continuously and consumes energy. In other words, it creates moment in respect to rotation movement of mill even although there is no movement. For that reason, it causes consumption of too much energy.

Several embodiments related to said ball mills are found in the prior art. One of them is European patent numbered TR2014/11178 and entitled “Stirring ball mill”. Classification class of B02C 17/16 in its abstracts reads as: “Mill comprises a milling container, a mixing spindle organized parallel to axis longitudinally in the container. A pre-crushing device connected to next part from product input provides a separation device, in other words, a sieve a grinding part protecting auxiliary grinding organs. The end of grinding aperture facing grinding part runs on static or dynamic opening protective side connected to rotating part or pre-crushing device fixed part." This application uses spindle inside mill for grinding operation. This operation causes much energy consumption.

Another example related to said embodiment is a European patent entitled “A method for operating a ball mill and a milling system” and numbered 2018/03399. Classification class A23G 1/00, the invention in abstracts reads as “The present invention particularly relates to a method for process of a viscose mass comprising solid components, being a fatty mass having solid components in a grinding system, and said system comprises a mixer and a grinding instrument and said method comprises following process steps: Feeding mass to be processed into a mixer; rotation of mass to be processed in a repetitive manner to a grinding instrument by a supply pipe from mixer for reducing size of said solid components in said grinding instrument and to mixer again by a return pipe by a replacement instrument; and additionally comprises following step: removal of at least a part of processed mass from the system by means of a branch duct provided on return line when predetermined grinding fineness is achieved; and supply of new mass to be processed into mixer and at least partial replacement of new mass to be processed at said grinding instrument by means of said replacement instrument and finally removal of at least other part of said processed mass from said system.” Said application provides improvement about material supply to and taking back from mill. There is no development about cascade movement.

While searching patents regarding matter, the file numbered US1671283A was encountered. This application is developed to break cascade motion and provide energy gaining. However, cascade is broken in action in the mill and some of balls reach over the peak point between mill body and inner wall and pours down from other (left) side and gives back some of moment it takes. Therefore, continuous moment is needed.

In said mill, balls move along peripheral and central projections of weight centre of balls falls onto centre and adequate energy saving cannot be achieved.

Also in said mill, pressure and friction environments of balls is compromised for sake of energy saving. It is pressure and friction that perform primary grinding work in standard ball mills. With falling rather hit conducts crushing (pre-grinding) works. For that reason, mill grinding performance in said application is seen as too low mill. This performance is also likely to be achieved by crushers conducting fine crushing.

Therefore, this and other applications can be shown as examples for above mentioned disadvantages. In conclusion, developments have been made in ball mills in parallel to technology and, therefore, new embodiments eliminating the above disadvantages and offering solutions to existing systems are needed.

Purpose of the Invention

Differently from the embodiments used in the present related art the invention relates to ball mills developed to solve said disadvantages and provide some additional advantages.

Purpose of the invention is to provide motion of balls in distant from centre at spiral tail and motion of spiral near centre in inner diameters during rotation by help of spiral structure of the mill. Therefore, moment to raise ball of same weight decreases and energy needed is also reduced.

Another purpose of the invention is to provide approach of material raised to drum wall to rotation axis in some times of full rotation stage or alignment with rotation axis in vertical direction during rotation motion by help of spiral form of mills bodies instead of being in full circle.

Another purpose of the invention is to increase energy efficiencies of ball mills and reduce negative impacts caused onto economy and environment by energy consumption.

A further purpose of the invention is to provide entire movement of cascade and thus bringing grinding stage near rotation centre by help of pressure. Thus, mill moment need is decreased.

Another purpose of the invention is to enable operation at lower speeds by help of spiral body and thus provide energy saving.

A further purpose of the invention is to enable operation of mill body not only in spiral form but other than circular form in different designs such as eclipse, cycloid etc. With such designs, the cascade is not stacked in certain place and will move inside mill.

The structural and characteristic features and all advantages of the invention will be understood better in the figures given below and the detailed description by reference to the figures. Therefore, the assessment should be made based on the figures and taking into account the detailed descriptions.

Brief Description of Figures

Figure - 1 shows front perspective view of spiral structure grinding mill.

Figure - 2 shows rear perspective view of spiral structure grinding mill. Figure - 3 shows schematic view of movements of grinding media located inside during rotation of grinding mill of the invention.

Figure - 4 shows schematic view of two spiral structures placed next to one another inside the mill.

Figure - 5 shows illustrative views of different spiral forms of inner volume of grinding mill of the invention.

Reference Numbers

10. Grinding mill embodiment

11. Mill body

111. Grinding media

112. Spiral structure

12. Mill driving members

Detailed Description of an Illustrative Sample

In this detailed description, the preferred embodiments (10) of the grinding mill being subject of the invention have been described in a manner not forming any restrictive effect and only for purpose of better understanding of the matter.

Said invention relates to spiral geometry instead of circular structure of mill bodies (11) in grinding mill embodiments (10) as shown in figures 1 and 2. Thus during rotation movement it is provided to make material and grinding media (111) raised at drum wall nearer to rotation axis during some times of one full rotation cycle or provide alignment thereof with rotation axis in vertical direction. The invention can also be applied in full ball and rod mills applied in wet, dry, autogenous, semi-autogenous, continued feed or batch methods.

Said grinding mill embodiment (10) is as shown in Figures 1 and 2. It comprises driving members (12) installed onto a certain ground and spiral geometry mill body (11) connected thereto in horizontal position.

With grinding mill embodiments (10) 3 processes are seen in material grinding operation. They are crushing, wearing and grinding by pressure. When mill starts rotating around its axis, grinding media (111) go up and after reaching a certain height, fall downward and provides crushing of material on the ground. While said balls move from down to up inside the mill, they are worn and ground due to frictions rolled over inner surface of mill. Finally, during cascade motion, materials on mid-part of grinding media (111) pile are subjected to pressure by grinding media (111) provided therein and thus grinding is provided.

Spiral geometry mill body (11) of the invention is a structure designed other than circular form. By this structure, grinding media (111) are not collected on one side of mill body (11) during rotation movement but change place in a manner to get closer to centre continuously. This motion is shown in figure 3.

Operating principle;

Figures 1 and 2 show perspective views of grinding mill embodiment (10). Material to be ground is fed into spiral geometry mill body (11). Then machine is run. When it starts running, mill body (11) starts to rotate around its axis with the driving provided by driving members (12). With this motion grinding media (111) therein start to move inside mill and cascade motion is started.

Motion steps of mill body (11) are shown in figure 3. Since diameters of spiral body mill body

(I I) are not equal, shape of grinding media (111) (cascade) changes during rotation. When motion starts, grinding media (111) are in the bottom part of the mill. Upon rotation of mill in arrow direction, grinding media (111) resting onto inner wall move upward. While grinding media

(I I I) move up, diameter of spiral body gets smaller and so it comes to centre immediately before starting to go down. Upon rotating a quarter tour in center within its body, grinding media (111) remaining motionless perform grinding operation with pressure. Flowever, since this time of remaining motionless is at a point rear centre, too little moment is needed.

Spiral structure (112) of mill of the invention prevents stacking of grinding media (111) on one single side during rotation and thus provides movement of all grinding media (111) close to centre during one quarter motion. Thus, driving members (12) consume less energy to rotate mill.

Alternative Embodiments:

Instead of entire of mill body (11) in spiral structure (112), outer part can be circular and inner part can have a separate spiral structure (112). In addition, instead of spiral geometry, designing in various geometries not circular such as eclipse, cycloid etc. can provide energy saving.

As stated, instead of single spiral in circular form as stated hereunder, placement of two or more spiral structures (112) facing one another can achieve the same purposes. As shown for circular form in figure 4, the spirals can be used without interlocking as well as interlocked. And in this way several spiral based mill bodies can be designed. Figure 5 can be examined as example to such designs. Raising and pouring motions of grinding media (111) of all designs may vary. Also rotated identical of the spiral bodies can be added onto one another. Thus, weight centres are provided on rotation centre too.

Invention in general;

All of stages of crushing by falling, grinding by friction and grinding by pressure as material grinding steps are performed. While performing such processes, cascade gets closer to centre at each quarter rotation and therefore system consumes less energy. Friction at 1 ^st quarter, pressure at 2 ^nd and 3 ^rd quarter and falling and crushing at last quarter provides grinding of the material.

Above mentioned components are calculated and designed separately for each process in line with mill grinding capacity and process needs. Spiral geometry mill body (11) of the invention can be sized in line with process needs and material input and output structures may vary.

Ball or rod mills as said grinding mill embodiment (10) are converted into the spiral structure and thus above mentioned purposes are achieved.