FIELD OF THE INVENTION
The present invention relates to a ball media dispensing system that prevent the blockages of ball media and enhances the efficiency of the mill by dropping the ball media only when necessary.
More particularly the present invention relates to grinding ball media feeding machine for ball mill.
BACKGROUND OF THE INVENTION
1. A ball mill of 75 T.P.H through-put was installed at a particular plant location for crushing the Chrome ore for beneficiation.
2. The Ball Mill is Barrel type centrally spout fed with grate discharge.
3. The starting Material (Ore water and grinding balls) is fed in the central spout feeder. From the discharge end sieves segregate materials of the requisite fineness which are discharged in the slurry pond.
4. Grinding media in the form of Fe-CR balls are charged daily, one a day due to attrition of the grinding media inside the mill. This is done manually. About 20-25 balls are charged in the mill daily. These are about 5-7 KG in weight and prolated in shape at the poles due to casting defects. This causes jamming at the feeding spout.
5. Due to this jamming the mill has to be stopped and dismantling the spout to clear the jam that takes about 4-5 hours. As this happens several times during a year, there is a significant loss of throughput due to this which amounts to @75 tons per hour.
6. These Grinding media balls are store on a platform adjacent to the conveyor carrying the media into the spout. These are manually dropped and a lot of effort is also required in feeding the balls one at a time.

Therefore the need for a Ball media dispensing system was felt which will prevent this blockages and also improve the throughput and efficiency of the mill by dropping the ball media only when necessary.
US patent US 2003/0234264 A1 discloses “Dry food dispensing system” in which a hermetically sealable dispenser for measuring and dispensing predetermined amounts of a granular product without breakage of the product. The dispenser comprises a container which can be filled with the product, and a flexible, rotatable, paddle wheel fixed within the container. The spacing between paddles of the paddle wheel form measuring compartments. The dimensions of the paddle wheel are such that the wheel forms a hermetic seal near one end of the container. A lid is provided to seal the upper end of the container such that the product is stored in an air-tight compartment prior to dispensing.
A prior art document US 25,93,089 relates to a construction for roller conveyers and in particular to a means of mounting the roller therein. The main object is to provide a roller conveyer of sanitary construction which has a minimum of dist collecting surface and which can be easily and quickly dis-assembled and re-assembled for cleaning.
It also provide a simple form of roller conveyor in which the rollers can be inserted one at a time without shifting the shaft with respect to the roller or without the rollers dropping out of place because of spreading rigid side members too much upon placing other rollers.
Another prior art document 1,028,589 discloses gravity carrier and particularly to those for transmitting merchandise of various kind of gravity. The primary object is to provide a means for locking the roller journals which will admit of the rapid assembliary of the parts without the necessities of providing for accurate fitting or adjustment.

Another prior art document US 6,964,355 B2 discloses a dry food is passing system. A hermetically sealable dispenser for measuring and dispensing predetermined amounts of a granular product without breakage of the product. The dispenser comprises a container which can be filled with the product, and a flexible, rotatable, paddle wheel fixed within the container. The spacing between paddles of the paddle wheel form measuring compartments. The dimensions of the paddle wheel are such that the wheel forms a hermetic seal near one end of the container. A lid is provided to seal the upper end of the container such that the product is stored in an air-tight compartment prior to dispensing.
Therefore in order to overcome the jamming of the feeding spout during manual feeding of the grinding balls prolated due to easting defects, a need for a ball media dispensing system was felt which will prevent the blockages and improve the efficiency of the ball mill.
OBJECTS OF THE INVENTION
An object of the present invention is to develop grinding ball media feeding machine for ball mill that prevents the jamming of the ball media during feeding and improves the efficiency of the mill by controlled feeding of the grinding ball.
SUMMARY OF THE INVENTION
According to the invention there is provided a system to develop a gravity feel automatic ball charging machine where the balls are to be discharged through an angled roller conveyer channels and dispensed through a paddle wheel type movable gate where a retarding mechanism will work on the penultimate ball to ensure that only one ball is dropped every time.

A suitable PLC and opto–electronics circuitry will be employed to count the dropped balls and control the mechanism. The entire system with closed loop control will be operated by a proprietary SCADA (Supervisory Control and Data Acquisition) system developed in-house.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Fig 1 –Image of a prolated ball media used for grinding. Fig 2 – Schematic drawing of the propose invention. Fig 3 – Isometric view of the schematic drawing of Fig.2.
DETAILED DESCRIPTION OF THE INVENTION
The machine described in herewith has been specifically designed to cater to dispensing irregularly shaped grinding media.
The Grinding Ball is cast from Ferro chrome Alloy, as the mill is used for crushing Ferro chrome Ore. This way after attrition of the grinding ball during the grinding process the composition of the output slurry does not contain foreign substances. During casting of the grinding media, due to casting imperfections etc the ball has a significant seam at its equatorial axis, and a significant prolated neck at the polar axis. This is due to the deterioration of the spout and channel in the cast from where the hot metal is poured.
Therefore due to this asymmetry conventional industrial ball feeding machines cannot be used.

A machine has been designed for specifically discharging these asymmetrical, grinding media.
The machine described in this document, will act as a repository or magazine containing up to 50 grinding balls or more. These will reside inside inclined channels. The sides of the machine (front and rear) will be made of iron mesh to enable easy cleaning and maintenance.
The media will be fed from the top from the left of the first, top most channel and
roll to the bottom of the channel by force of gravity. Whereupon it will fail upon the
next channel which is inclined from the right to the left and roll downwards through
other staggered channels till it comes to the outlet of the machine.
Each channel will act as a corridor to guide the rolling media downwards using
gravity.
To ensure that the balls do not get stuck due to their asymmetry, the floor of the channel will consists of hollow steel tubes, capable of rotating about their central axles and with sufficient space from adjacent tubes to allow un hindered rolling of each.
There will be bearings inside that the tube around the axle to ensure smooth rolling
of the tubes.
The axles can be removed from the sides through simple arrangement such as
butterfly nuts or similar arrangements, to enable quick maintenance and
replacements.
The angle of inclination of the ramps/channels through which the media rolls can be adjusted to calibrate to the optimal speed of rolling of the balls. There will be a spring loaded trapdoor if required at the ends of each channel to decelerate the momentum of the balls.

At the lowest ramp there will be a dispensing mechanism/gate to ensure that only the first ball at the gate is dispensed while the bell next to it is prevented from dropping out.
This will be done through a braking arrangement. A mechanical gripper operated either by short stroke pneumatic pistons or by electro magnets will be placed 10-12cms from the gate. When the last ball is positioned over the gate the penultimate ball will be held by the brake shoe like arrangement operated by the electromagnet / pneumatic pistons. Only when the brake is engaged the latch beneath the gate will be opened.
The gate will be of a carousel type and have 4 doors, each door perpendicular to the next one connected over a central axle.
As the latch is disengaged, due to the weight of the ball the carousel mechanism will rotate by 90 degrees, the released ball will fall through a tube vertically downwards. Inside this tube an opto-electronic counter will count the number of ball dispensed and give its feedback to the PLC controlling the machine.
As soon as the falling ball is detected the latch of the carousel gate will be engaged, and the ball retarding mechanism, operated by pneumatic or electro magnet will be disengaged. This will allow the penultimate ball, (now the first ball) to get positioned over the gate, ready to be released in the next operation of the gate.
The PLC which controls the machine will receive inputs in the following ways.
1) From a Timer operated by push buttons connected to the PLC.
2) Through a remote SCADA system developed for this purpose which will heuristically determine the time and number of balls to be dispensed after evaluating the throughput and output quality of the ball mill from a particle size density (PSD) sensor.
3) Manual discharge by operating the gate locally by Push Button.

The PLC system will also have other features to ensure fall safe operations and provide data such as number of balls dispensed and number of balls remaining in the machine and generate pre-configured alerts and alarms etc.
The grinding ball feeding machine described in this document is designed to feed in the ball media one at a time.
The intervals between releases of each grinding ball can be adjusted using the associated PLC and SCADA.
The dispensing of the ball media can also be run in automated mode by analyzing the output efficiency of the ball mill obtained from a particular size density meter at the discharge sump, and heuristically determine when and how many additional grinding media needs to be dispensed if any.

We claim
1. A grinding ball media feeding machine for ball mill comprising:
- a chamber fabricated by steel member in the sides and having an opening or
acting as hopper at the left side of top for entry of grinding ball into the
chamber wherein channels are configured in inclined manner between the
sides with opening at the lower end of each channel for passage of grinding
ball media in the next channel just below the previous one, inclined in
opposite direction;
- having an opening in the downstream end in the same manner, the said
channel comprising plurality of hollow steel tubes mounted side by side over
axles fixed on the channel forming a roller conveyor for movement of
grinding ball in criss-cross manner from top platform to bottom using force
of gravity till it reaches at the outlet which is provided with a carousel type
dispensing gate operated using gravity and electromagnetism instead of gear
arrangement of the prior art.
2. The grinding ball media feeding machine as claimed in claim 1 wherein the gate is of carousel type and having 4 doors, each door perpendicular to the next one connected over a central axis.
3. The grinding ball media feeding machine as claimed in claim 1 wherein the rotation of gate door is operated by brake shoe like arrangement operated by the electromagnet / pneumatic piston.

4. The grinding ball media feeding machine as claimed in claim 1 wherein the interval between the grinding ball is controlled by PLC and SCADA.
5. The grinding ball media feeding machine as claimed in claim 1 wherein the floor of the channel comprises hollow steel tubes mounted on central axles by ball bearing for easy rotation.
6. The grinding ball media feeding machine as claimed in claim 1 wherein the axles are mounted in the holes of channels and removably fixed by nuts.
7. The grinding ball media feeding machine as claimed in claim 1 wherein the tubes are fitted sideway so as to allow unhindered rolling of each tube.
8. The grinding ball media feeding machine as claimed in claim 1 wherein the front and rear side of the machine is provided with wire mesh.