US1690712A - Pulverizing mill - Google Patents

Description

. Nov. 6, 1928.

L. C. BONNOT PU ERIZING MILL Filed May 2 1925 2 Sheets-Sheet 1 101/13 6. Bail/lat Nov. 6, 1928. 1,690,712

L. C. BONNOT PULVERIZING MILL Filed May 23, 1925 2 Sheets-Sheet 2 gwoemtoc Leafs 6. 190/2120;

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I 25 considerably Patented Nov. 6, 1928.

UNITED, STATES 1,690,712 [PATENT oFrlcs LOUIS C. IBONHOT, F LOUISVILLE, OHIO, ABSIGNOB TO THE OI CANTON, OHIO, A. CORPORATION 01' OHIO. 3

Application filed lay :33,

The invention relates to a rotary drum grindin or pulverizing mill partly filled with ba ls, pebbles or. the like; and the object of the improvement is to provide a ma- 5 chine which can be operated at low speed and will continuously deliver a predetermined unvarying powdered product, without any adjustments or changes in the machine and without the" use of separating or I l'U grading apparatus.

The mproved mill is well adapted for pul; verizing small lump or slack coal for supplying powdered fuel directly into a furnace or a fuel feeding system, and the invention is illustrated and described with reference to such a use of the mill, without intending to limit it thereto.

In mills of this type an axial'tube extend-- ing into and sometlmes through the mill has 2 been used for withdrawing the powdered product from the drum through one end of the tube; and such mills have een designed for and generall operated with such a quantity of rin ing balls as will occupy dess than one-half the cavity t the drum. Y

Mills of this kind have sometimes been operated at such a speed and with such a frictional engagement of its peripheral wall, supplenientef y the action of centrifugal force, that the grinding balls are carried upward on the rear side of the axial tube and thence forward over and above the same, so as to flow freely downward throu h space, either against the peripheral w of the drum-or upon the grinding balls in front of thetube a For the pu of increasing the grinding efliciency 0 such a mill, it has been pro- 40 posed to provide a stationary deflecting w'all extending from end to end directly upward from the rear side of the axial tube to the peripheral wall of the drum, to serve as a bafile or anabutment for the grinding balls and ground material 'movin upward the rear side of the drum, to eflect the same from falling forward so as to shower downward upon the ascending body of balls and raw material in rear of theiaxial tube, for

a direct grinding action therewith.

' 'In the operation bf both ofsuch kinds of mills, however, the grindi balls return to the lower art of the drum y falling-heel downwf ,more'or lees separated from each important purpose is. atta1 n,

same 11 mas. Serial mfaaemmovementl but remain in rollingand therefore grin ing contact with each other, or v with the intervening raw material, 'soas to constantly act to grind and reduce the same.

It has also been found that the most efiicient action in mills of this kind is obtained by filling substantially one-half of the'cavity of the drum with'grinding'balls, androtatin the same at such a speed and with such frlctional englagementwith the peripheral wall, that the alls are carried u ward in the rear side of the drum so as'toro downward and forward in grinding contact with each other through the-central or axial re "on of the drum; without being separate from each other, or diverted from or impeded in their most eflicient grinding action, by the presenceof a'bafile wall or a suction tube 30 in the middle or central region of the drum. L

It is,-therefore, ,an important purpose of the present improvement to construct and arrange the rotary drum, andthe material feedin and withdrawing devices, so as to leave t 'e entire lower and upperrear regions in the drum, including the central or axial region thereof, freeof obstructions; sothat the drum may be filled substantially half full of grinding balls, and ma be operated so that the balls will be carrie upward and rearward and will then rollupon themselves downward and forward through thefaxial region of the drum, for the most efficienta grmding'action upon the material which is among the balls. Y

- 'As a part of the present im rovementjthis by sending dust collecting means, which may in the form of a tubular screen, inthe upward, forward region of the drum, and mounting the n a flatzhollow support located in one en of the drumrand extending'upward from an axial suction tube leadingoutward an opening in the'sameend III of the drum. v

In combination with such duet collectli llfi means, it is preferred to provide mate feed chute and suction exhaust tubes, re-

means' for the drum inthe form of retain %ned chute, for discharging material an inc into the drum through an axial opening in the other end thereof; and the axial openings inthe ends of the drum are enlarged so as to form free annular ports around vthe the suction exhaust tube.

Apparatus embodying the. present invention is illustrated in the accompanying drawings, forming art hereof, in which- Figure 1. is a si e elevation of th .v 1

proved ap aratus, showing the rotary drum and feed 0 'ute in axial section and 1 end a flange Fig. 2, a crosssection GlBVQtlOIlOf the apparatus, on line 2 2, Fig. 1;

Similar numerals -'efer to like parts throughout the drawing.

The rotary drum 3 may have on each ripheral track band 4 riding upon. wheels 5 mounted on shafts 6; and

the drum may be rotated by a central, an

.mounted on one of the shafts 6, which may be driven from-any suitable source of ,power. A central'openin is provided in each end of the drum, and t'e same may be formed by the inwardly flared conical collars 9 and 9; and a'. downwardly inclined tubular chutelO is mounted so that its dischar end will rotrude into but not through t e opening ormed by the collar 9, for feeding material into the drum without extend- -.ing' into the same.

A suction exhaust tube 11 is mounted, as on .a pedestal 12, at the other end of the tube, so that one end will extend into and through the opening formed by the collar 9' whence the shape ofithis tube is oh; iged to a flat hollow supporting arm 13 extending i upward and forward within the drumimmediately adjacent to the end wall thereof.

On the upper end of the hollow-supporting arm 13, is formed. a tubular elbow 14; in which is secured one end of a dust collecting receptacle 15, which may be in the form of aslotted screening tube, as shownyand i is located in the upper forward region of t e drum, so as to leavetthe remaining 're-.

' i gions of the drum freefor the unobstructed dust by suction-from the ism' 2 the r i ad disc through outlet p1pe"1 8-1'ea from the vements of the material. f -I [if-T h r outer 'llauSt tube 11'ma be connected di grinding balls and the raw' end of the suction exwithin the-inlet orifice of an. exhaust fan 15, which in "turn may be directly -con-- iected with a motor 17, for exhausting upper/forward rear the same fan. 4 t A The described construction and arrangethereof,-

ment of the apparatus, leaves the middle region of the rotary drum without any.

impediment for the free movement of the grinding medium through the same.

In the operation ofthe appartus, the no- .tary drum is filled" substantially half full of grinding balls, and the drum is rotated at such a speed as will carry the balls upward in the rear side of the drum only far enough as to roll upon each other'downward ing. It has been found that a drum having a diameter ofsome 4 ,ft. 6 in. and a ball charge filling substantially half of its caviltiy, may be rotated: at the rate of 28 R. P. to accomplish the desired. result which has been described.

' Raw material is then fed into the amthrough thefeed chute 10, which may be in the form of small lump,.nut or slack coal,

until the same fills all the interstices between nular-girt gear 7, meshing with a pinion 8 the grinding balls and in addition thereto may fill something more thanone-half of the cavity of the drum; whereupon the grinding action of the balls upon the material and of the material upon itself serves to reduce the same to a fine or 'impalpable powder, which rises by its own buo ancy into the region of the drum above an forward from the mass of grinding balls .and raw material in the lower and rear regions there- The speed of rotation'of the drum is so slow that verylittle if any unground material rises into the upper forward regions of the drum, from which the powdered matemitted by the entrance of air-into the drum through the annular ports the ends takethe lace ofthe air and dust exh iisted there om and the induction of air through these ports into the drum also prevents the ejection of much, if any,

dust through the same.

The'a'nnular' tion tube is pre erably formed less in width than'the size of the grinding balls, so as to prevent any of the same from passing ort around, the? exhaust sucoutward through "the same; and when the end of the feedwhute 10 is eccentrically positioned in the opening of the collar 9, .a shield 19 may be" secured to the chute adjacent to the rim of the conical collar for preven through same, which shield may provided with apertures 19' tltile1 'fiijw ermo're e 111- of airinto the drum. F

the ejection of grindin balls receptacle extendin stantially across the upper region of the wardly flared shape of the conical collars 9 and 9 serves to retain the grindingballs in the drum.

It will be understood that the fineness of the powdered material which is withdrawn from the drum, may be controlled by the speed of the exhaust fan and the resulting rate of the movement of air from the drum through the dust collecting receptacle.

I claim:

1. A pulverizing mill including a rotary drum with a central opening in each vend thereof, grinding media as balls, filling substantially half the cavity thereof, feed means for delivering raw material into the drum through oneend openingthereof, and suction exhaust means including a collecting longitudinally and subdrum and a radially extending flat hollow support adjacent the other end of the drum roviding communication from the collectmg receptacle through the other central end opening for withdrawing dust from the upper region of the drum through the other end opening thereof, there being air inlet ports 1n the ends around the ,feed and exhaust means, and the middle region of the movement of drum being without impediment for the free the grinding media therethrou h. F

2. pulverizing mill including a rotary dru'm with a central openin in each end thereof, grinding media as ba ls, filling substantially half the cavity thereof, feed means for delivering raw material into the drum through one end opening thereof, and suction exhaust means including a tubular collecting screen extending longitudinally and substantially across the upper region of the drum and a radially extending flathollow support adjacent the other endof the drum roviding communication from the collect:

mg screen throu h the other central end opening for withdrawing dust from the up per region of the drum throu h the other end opening thereof, there being air inlet ports in the ends around the feed and exhaust means, and the middle re ion of the drum being without impediment or the'free movement of the grinding media therethrough. Y

In testimony that I claim the above, I have hereunto subscribed my name.

LOUIS o. BONNOT.

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