US1619295A - Apparatus for and process of reduction of finely-divided material - Google Patents

Description

1, 1 ,2 5 March 1, 1927. w. GARDNER 6 9 9 APPARATUS FOR .AND PROCESS OF REDUCTION OF FINELY DIVIDED MATERIAL Filed April 14, 1926 INVENTOR Q /M W W flZZ/x Patented Mar. 1, 192' 7.

UNITED, STATES PATENT- oFFlcE.

WILLIAM GARDNER, or CLEVELAND, OHIO.

APPARATUS r03 AND rnocnss or nn-noo'rron or FINELY-DIVIDED MATERIAL.

Application filed April 14, 1926. Serial No. 101,871.

This invention relates to the process of obtaining and separating finely divided granular material by what is known as a dry grinding process as distinguished from 6 a wet grinding process for thesame purpose.

not require expensive apparatus and ma-i chinery, and which eliminates the use of 1 screens and numerous conveyors and which has comparatively few parts to wear or get out of order. 1

A further object of the invention is to provide a process for separating finely di- 2 vided material in which the fines are removed from the grinding unit as made thus preventing the cushioningof the unground material within the grinding unit.

Further and more limited objects of my 2 invention will appear as the description proceeds and by reference to the accompanying drawing in which is disclosed a somewhat diagrammatic view partly in section and partly'in front elevation of the apparatus used In connection with my process.

In the accompanying drawing I have disclosed a short type pebble mill 1 which is fed from a hopper '2. The material is ground or crushed in the pebble mill 1 and connected with the pebble mill is a conduit 3 which is connected with the top of a settling and classifying chamber 4 having baflles 5 and 6 adjacent the inlet. Below the chamber 4 are a pair of conveyors 7 and 8 which are driven in opposite directions as indicated by I the arrows. The settling chamber is also provided with a plurality of spouts 9 having valves 9 through which the material may be withdrawn and tested. The spouts 9 are so constructed that they may be positioned to deliver material either to the conveyor 7 which returns the oversize material to the grinding unit or to the conveyor 8 which removes the finished product. Connected to-the upper end of the settling chamber is a conduit 10 having apairof diverging delivery branches 11 and 12 de-' livering to the lower end of a. filter chamber 13. The filter chamber 13 is an air filter of standard type having flat screens or bags. Connected with the upper end of the filter chamber 13 is a suction fan 14 driven by a variable speed motor 15.

The material tobe ground is delivered into the hopper 2 and thence into the pebble mill and the fines are removed as soon as formed. It has been found by experiment that the greater partof the grinding in the usual type pebble mill is accomplished in the first .five feet'of the mill and considerable power is wasted due to the cushionin 'action' of the finely divided particles on t e oversize or unfinished product within. the mill. According to my process I make use of a short type of ball or pebble mill and remove the fines as soon as formed. This is accomplished by an adjustable current of air through the grinding machine, the; velocity of the air being suohgtha-t the fine particles are held in suspension thus preventing the cushioning of the unground material within the pebble mill. This current of air may be adjusted so that a classifying of the different size particles will result as only particlesof the required size are removed from the grinding unit. The pebble mill is also provided with an adjustable air inlet opening shown at-16 whichserves as a further means of regulating the flow of air through the" apparatus, the main adjustment of this current of air being controlled by the speed of the motor 15. The fine particles will be delivered into a settling chamber 4 which is of such a size that the velocity of the air current will be reduced thus allowing a settling of the material ,in suspension. As hereinbefore stated this chamber is provided with spouts 9 for removing this settled material which will be of a gradually diminishing size further along the settling chamber from the inlet. Should the material withdrawn from any one or more of these spouts be oversizethe same may be delivered to the conveyor 7 and returned to the grinding unit and if the material so large volumes of air can be admitted through an adjustable air inlet opening 16 at lower velocity when fines are required and in the opposite ratio for coarser material; and it will therefore be seen that this process is a classifying process in direct connection with the I Cgrindlng medium capable of delivering size claims.

particles from the grinding element. Another feature of my invention not heretofore mentioned is that the filtered air is not returned to the grinding unit but is discharged into the atmosphere. Fresh air is drawn in through the opening lfi and takes up the finely ground particles as soon as created, the size of the particles held in suspension depending upon the velocity of the air current, thus preventing any cushioning of the unground material within the grinding element. The velocity of air through the apparatus is regulated by the speed of the motor and also by the size of the adjustable inlet opening 16.

My process Is Well adapted for handling ractically all dry ground materials such as ne black, cement, feldspar, gypsum, graphite,-limestone, marble dust, phosphate rock, shale, talc, igments and all kinds of natural and artificial abrasives.

It will be clear that I have provided a process which will accomplish the objects of the invention as hereinbefore stated, and it is understood that my process is to be limited only in accordance with the appended Having thus described my invention, what I claim is I 1. The process of reduction of finely divided material which consists in grinding material. in a grinding unit, removng the fines from the grinding unit by means of a current of fresh air of low velocity and large. volume before all the material has been ground to its finest condition therein, pass-" ing the fines through a settling chamber and returning to the grinding unit the oven sized particles and passing the sized particles through an air filter without the return of the air used as the conveying medium to the grinding unit. a

2. The process of reduction of finely divided material which consists in grinding coarse material in a grinding unit, removng the fines from the grinding unit by means of a current of fresh air of low velocity and large volume, delivering the fines to a settling chamber, withdrawing the fines still in suspension from the settling chamber and passing the same through a filtering chamber and discharging the air into the atmos phere.

3. The process of reduction of finely diminishing velocity towards the outlet and 76 passing the same first through a settling chamber-and then through a filtering chamber without the return of the air in closed circuit to the grinding unit.

4. The process of reduction of finely divided material which consists in grinding coarse'material in a grinding unit, removing the fines from the grinding unit as soon as formed and assing the same first through a settling cham er and then through a filtering chamber by means of a current of fresh air of gradually diminishing velocity towards the outlet without return of the air in closed circuit to the grinding unit and discharging the air used as-the conveying medium into the atmosphere.

5. The process of reduction of finely divided material which consists in grinding coarse material in a grinding unit, removing the fines from the grinding unit as soon as they are formed by means of a current of air, passing said current of fresh air of low velocity and large volume through a settling chamber and then throu h a filterin chamber and discharging the filtered air 1nto the atmosphere and returning to the grinding unit the over-size particles independent of the flow of the air'used as the conveying medium.

6. The process of reduction of finely divided material which consists in crushing coarse material in a grinding unit, with drawing the fines from the grinding unit by.

means of a current of fresh air of low velocity and large volume and passing the current 0 air through a settlin chamber and then through a filtering cham r and dischar g the conveying medium into the atmosp ere and returning the over-size articles to the grinding unit independent 0 the flow of the conveying medium. v

7 In an apparatus of the class described, a grinding unit, a settling chamber connected with said grinding unit, a filtering chamber connected with said settling chamber and a fan connected with said filtering chamber anddischarging directly into the atmosphere, said grinding unit having an openin therein communicating with the atmosp iere, means for delivering material to said grinding unit, means for operatingsaid fan to cause fresh air to be drawn in through said opening in the grinding. unit and delivered successively throu h said settling chamber and filterin cham er and dis charging into the atmosp ere.

lbs

8. An apparatus as set forth in claim 7 having means for varyingthe velocity of the having-means for returning-to the grinding conveying medium whereb to remove difunit the oversized particles separated in the ferent size particles from t e grindin unit. 39 settling chamber, said means being inde- In testimony whereof, I hereunto a my 5 pendent of the path of flow of the conveysignature.

ing medium.

9. Anapparatus as set forth in claim 7 I W. V

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