US2376820A - Ball mill - Google Patents

Description

2 She'ets-Shet l E. SAUMENICHT I BALL MILL Filed Jan. 11 194? May 22, 1945.

all! II May 22, 1945 E} SA UMENICHT BALL MILL Filed Jan. 11, 1943 2 Shets-fiheet-Z INVENTOR Smmzmcur ATTORNEY Patented May 22; 1945 s v i BALLMILL i i 4 Ernest Saumenicht, Ohatham, v

. ApplicatlonJanuary-ll,194 3; Serial No; mils-5 5 I l 3' Claims. (emu-7o)" Thisinvention mega it mills, and aras; ularly to conical ball mills. r a I An object of the invention is to provide an improved conical ball mill that 'will'have an in creased output of material ground'to a maximum fineness. I

' It is another objectof the invention to provide animproved conical ball mill wherein the pulp is more readily' discharged through the discharge throat of the'milly h f It is a still further objectto provide a conical ball mill that has particular merit in wet grinding in that the pulp level can belowere'd substantially below the discharge'throat' of the mill and thereby increase the maximum eiliciency of the' mill.

'It is another object of the invention to provide a. ball mill thatis adaptedio'r either wet'or dry grinding wherein the i'pulp" is prevented from building up at the discharge throat by permittin removal of the pul'p ff rom 'the "discharge throat at a level below the 'maxin'i'umnormal heightbf the pulp in the discharge throat. It is another object of 'the'invention to provide a discharge throat foraconic'al 'ball mill thatisconstructed andarranged to lower the pulp-level at the discharge throat to prevent the material from crowding at the dischargethroat and thereby'permit free discharge thereof to increasethe capacity of the ball mill, the discharge throat being also constructed and arranged in a manner that the pulpthat discharges through the discharge throat below=the-lowest point of the dischargeopening is carried bodily around'the discharge throat to'p'ermit its gravity discharge into asuitable carrier; g

It is another object of the invention tozprovide a conical ball mill having means in the discharge throat for bodily liftingthe pulp from the discharge throat and permitting the same to discharge therefrom by means of gravity.

A further object .of this invention is to'provide a. conical ball mill having a discharge throat therein that is constructed and arranged in a manner that the pulplevel is substantially lower than the normal overflowlevel at the discharge throat sothat themassing of the pulp at the'disg charge throat, is relievedwhen used for, either dry or wet grinding; the'lowering of the pulp level being accomplished without effecting the efliciency of the grinding operation in the ball mill and without altering the general conical shape of the discharge end of the ball mill to permit maximum grinding or the material to obtain maximum fineness of the material before it is discharged th h th d ch e thr t: 1

Further objects and advantages will become ap the drawings and the following-dd parent tromscription, v

In the drawingsz i a h Fig. 1 is a side elevational view of a conical ball mill. I

Fig. 2 is a longitudinal cros s seotional view of a conicalball mill havingthe improved discharge throat of this invention. Q h i i Fig. 3 is an enlarged end elevational view of the discharge grates in the discharge throat taken substantially along line 3'3 of Fig. 2. v

Fig. l is an enlarged cross sectional view taken alongline.44 of Fig,2 a i i Fig. 5 is a cross-'sectionalview oflaportion of the improved discharge throat showing aslightly modified arrangement thereof.

r Fig. 6 is a cross-:sectional-view of another modified arrangement of the discharge throat'for the ballmill. i Fig. 7 is a transverse, cross-sectional view of a alonglinellofFigfil p In this inventionthe'ballmill l0 consists offa discharge throat disclosed in'Fig 6 and'is taken shell II that may be fabricated in any conven-. j

tional manner. The shell consists of a' conical inlet end l2, a cylindricalpo'rtion' l3 and a conical discharge end M. The conical discharge end I4 is constructed so that th'e'inner surface of the shell forms an angle of approximately 30 with the axis of themill Hi1 A liner I5 is provided within the shell I I that may be constructed in sections to permit removal and replacement of any portion of :the liner that should become worn or damaged. A trunnion IGhaving an opening l1 therethrough is provided on the inlet end {2 of the shell ii, and a; trunnion 21 is provided on the outlet or discharge end: of the shell ll. These trunnicns I6 and 2'! are supported in suitable bearing members -18 and I9, respectively; whereby the shell H is rotatably mounted.

A gear 20 is secured to the shell H around the discharge and I4 thereof that engages a pinion 2i providedon an end of a drive shaft22 extending from an electric'motor 23. The pinion 2| and the gear 20 may be either'of the spuror herring bone type. Also the direct drive connection from the electric motor 23 may be changed to' a belt drive, or any other suitable mechanism, for rotating the ball mill. mean he provided. i a

The inlet opening n for the ball mill in has a feed chute associated therewith f for feeding material into the ball mill 1.; The material discharged into the .chute zimay be controlled in any suitableman'ner to regulate the quantity 7 whereby the'finely ground material has a tendof the material that is fed into the ball mill and v ency to accumulate further back 7 toward the thus regulatelthe rate of discharge of the mate-j center of the mill and thus reduce-the operating. rial from the ball mill. The ball mill I0 is proefficiency of the mill.

I vided with a discharge opening '25 provided in 5 Inthis invention there is provided an irnproved v the cone-shapedend wall l4of the shell II that discharge throat for a ball mill that'will permit has a discharge flange 26 associated therewith. I "dischargeof the, pulp :from a lower level than for discharging pulp into a suitable carrier. would normally occur in' the overflow type of dis-f The description of theball mill just given is a charge arrangement,.and When the mill is used gene'lfal i iifi l i. .7 t .t 7 that is adapted for iherwet or dny grind'ingr se retes when used for drylgr indiflg; It is-well-known that conical ball mills con-1 Thedischarge 'throatp3flisprovided with a structed and arranged in a manner disclosed in i plurality of triangular shaped grates 3| that are t app haverthel peculiar feature T 12 eshaped arcuately transversely so that when'a segregating the balls in the mill so that the lar g'e 'gffiuiality of the grates 3| aredisposed in engageballs are disposed within the largestdiameter cinentwvithaonefianother thatacone-shaped grate r of the ball mill and as the diameter of the shell; .memberis provided. Each of the grates 3| are of the mill decreases toward'thedisliargififbefi ing that the balls automatically seg e fi'e'f mm- 1: dischargefithroat 30 of the ball mill and are spaced selves so thatthesizeofthe ball decreases-toward 20 from the wall of the discharge endof themill by s trie fifslia ga t rhts aiiaiteaeat sim meats;st angestzwdmeaa dygs ment with the liner 5 and the race eyicflof 'tPTe giatEsQ sinarrgnnrem e ate a is to' be dischargedfrdir'r as was a i it eerates 3=1land l?513 plVenbabmgignaoi th he charger-opening. ar-scremM-tsrrow r .edvovge g pex end of the discharge throatg a o t ,preyeht OfithbfillSfifOm within -1 h 1 1 in'ibroveddisoharge throat; usedifor wet grind+ mg, the 'material sisiifiedrsintowtheleballimills ffl through theeihletmrofeedaopening *l'fLc: a l-meamill,

7 t rGaPWHi h sithefn mar-pr cti Abra? teaser-wan df' the discharge 'e 7 whenaheebammmwstmsinvention; Fwithcthe will carry it from the mill.

reaches the lowermost edge of the opening 25 whereby the general forward motion of the pulp However, in this invention the pulp can-be removed from the mill at a lower level than that established by the lowermost edge ofthe discharge opening'25;

. In previous conical mills it was necessary'to lower the position of. the discharge opening and thus lower the general level of the pulp in the mill ifa lower pulp level was to be obtained. This condition substantially reduced the output capacityof theconical mill because to reduce the general level of the pulp it was required that less material be fed through the mill.

In this invention, however, the openings 35 in the grates 3| permitthe pulp topass into the spaces 35 when they are disposed at a, level be neath the discharge opening 25 so that the pulp will be removed from within the interior of the ball mill at a lower level than that normally established by the lowermost edge of the dis charge opening 25. This permits relief,of the crowding, or packingof the pulpat the discharge throat, because it has a greater surface area of escape from the'throat. It will be noted, how-- ever, that even though the pulp levelis lowered in the mill, and can be lowered to the point indicated by the dotted line 4|, that the general level of the pulp in the forward, or feeding end of the mill has not been lowered. Since the general level of the pulp has not been lowered the volume of the material capable of being handled in the mill is not reduced and the capacity thereof remains the same, andis actually increased because the pulp is removed from the discharge throat before there is any tendency of the pulp to pack at the discharge throat. I

It is, of course, understood that the ball mill I is rotating during its operation, and as viewed an annular ring 45 issecured to the end of the wall 14 of the shell "whereby a space 35 is provided-between the grates 3| and the annular ring -46, and the vanes 32 engage the annularuring 45 to'supportthe grates 3| in the throat 30. The

support trunnion Ila may be carried bythe annular ring in place of being upon the shellwall M, as "heretofore described. The operationof the modified form of structure is identicalas heretofore described regardless of whether a dry grinding or wet grinding operation is being performed. 7 i

- In Figs. 6 and '7 there is shown a modified arrangement of a throat opening for a ballmill wherein thepulpis picked up bodily from" the lower portion of the mill and carried to the upper portion to be discharged by gravity in the same manner that the vanes 32a, heretofore described,

pick up the pulp within the space '35 and carry it to the top of the mill so that it will be dis-i charged by gravity. In the arrangement shown in-Figs. 6 and 7, the lining andshell 5a of the from the right-hand end of the mill shown in Fig, 2, is rotating in a clockwise direction. Therefore, the pulp that discharges through the openings 35 in the grates 3| is picked up by the vanes 32a and carried upwardly bodily until the'vanes pass over the horizontal center and begin to be disposed angularly relative to the horizontal as shown in the upper portion of Fig. 3. When the vanes 32a are in the position indicated by the vane 32aa, see Fig. 3, the pulp will slide forwardly on the vane over the blank wall surface 35 of the grate 3| and thus be discharged through the flange 25 adjacent the opening 25, this discharge, therefore, being by gravity flow.

When the ball mill is to be used for dry grinding the operation thereof will be identical with the operation just described.

- In Fig. 5 there is shown a slightly modifie form of the structure of the throat of the ball mill of this invention. It will be noted in Fig. 2

I that the spaces 35 have been-provided by indischarge end of theconical mill is continuous to the-discharge opening 5|, a discharge flange 49 being positioned adjacent the discharge open ing 5|. A plurality of vanes 52 are positioned radially within the discharge throat 55 in engagement with the wall 50. A grate 53 is positioned adjacent the forward ends of the vanes 52 and is provided with a'plurality of openings 54 through which pulp can pass through the discharge open- Since the vanes are secured to the wall 50 they will, of course, rotate when the ball mill'rotates-f Th'e pulp passing throughthe openings '54'in'thegrate53 will be caught by thevanes 52 and moved bodily'upwardly until the vanes 52 have a downwardly inclined angle' as indicated bythe vane 52a, shown in Fig. '7, whereby the pulp will slide downwardly along the vane against the wall 50 to the discharge opening 5| and thereby be discharged from the ball mill by gravity flow.

, It will be readily apparent that the vanes 52 will maintain a lower pulp level at the discharge 3 throat 55 than if the pulp was permitted its normal flow through the ball mill until it was forced I to overflow the lowermost edge of the opening 5|, and this would be true whether the ballmill was used for dry or wet grinding.

In the foregoing description it will become apparent that the pulp level in the ball mill-can readily be controlled by the position of the inner-,

most openings 35 in the grates 3|, or by the in nermost ends of the vanes 52. The position of these openings, or the ends of the vanes, is predetermined according to the size of granule that is to be discharged from the ball mill. Also, the position of the pulp level could be made readily adjustable by providing suitable means for closing certain of the rows of openings provided in the grates 3|, or by controlling the position of the innermost ends of the vanes 52, all of which changes in pulp level at the discharge throat can be controlled without reducing the general level of'the pulp in the mill, or without reducing the discharge capacity of the mill regardless of whether it is used for wet or dry grinding. Also, the construction of the discharge throat in this invention reduces the horizontal travel or the pulp through the mill without reducing the efficiency of the grinding operation because the general level of the mass in the mill is above the pulp level at the discharge throat. I

While the apparatus disclosed and described

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