US2651471A - Centrifugal grinding mill with abrasive liner and angularly disposed feed conduit - Google Patents

Description

Sept. 8, 1953 H. A. NOLL CENTRIFUGAL GRINDING MILL WITH ABRASIVE LINER 5 AND ANGULARLY DISPOSED FEED- CONDUIT Filed Oct. 7, 1950 J5 J2 J2 JYez'rz rah/317172014 A/olL Io/e rz m Patented Sept. 8, 1953 CENTRIFUGAIA GRINDINGGME WIIEH 'SIYEQL'JNERIIAHD ;DI P ;S..ED

GONHUIT Heinrich Arnold "Noll, Duesselglori; ermany;;as signer toH'.%H:and H. Manufacturinggcm, GhicagogJlLya corporation of-i-llin'ois 'sApplicationQctober 7, 195,9, SerialNo, 1;8l-,010

,eln Germany Fcbruaryg13 1950 'iil fllaim. (Clk 24l- S6) "The invention relates to.centrifu'g'aligrinding v mills or [hammer .mills and the like employed 1 for grinding or pulverizing 'ores, coalygrain'and other materials including those' of a fibrous na- Lturesuch as wood, 'andthetfeaturesqof'the'in-' '"vention. and 'the principlcs 'involved may-beembodied in home uti1ity:devic es such as garbage disposal machines as well as devices' forvarious industrial purposes. In a' more particular sense the invention is concerned with*a'special'attrition' or 1 grinding surface and effective "and efiicient processing .ofzmaterials' toy'be ground orrrejduced toa pulverized state throughtheme'diumpf cerftain specialconstructions.

. Centrifugal 'or hammer mill "grinders'perform their "functions r ly" by impactbetween tthe "rotor elements, (blades (01? hammers) and'the pieces or "particles of m-aterialito be reduced to "smaller'pieces orjparticle size and-partlyibytim- "pact-of ithe pieces-"or particles against f-t heinsidesurfacesof the' housing' or body "off-the mill --iorming the grin-dingchamberfthe pieces-'orpary-ticles 'being "batted against the interior wall surfaces or the -'-grinding chamber-under: fhigh 7V9- locities-imparted "by" the whirling "vanes,-blades orhammers-thereby to lee-shattered ,or broken. 1 Of *ccurse there =-is interpartielef orpiece impact and attrition --and a "certain amount of grinding occurs through frictional interengagementof the pieces or-- particles with the grinding chamber 'walls--asfthose-pieces -or particles are-whirlecl -or batted about in the -=grindi-ng chamber. *Fric- *tional contact of the pieces and particles -with i the grinding chamber walls also results ingrinding s away the walls themselves and such wear and tear upon the walls -is often very great indeed causing breakdowns and frequent shutdowns forrepair and replacement of the worn or otherwise affected par-ts. The-expense ofre- --pair and replacement is very high indeed-in some mills of this type depending-on the material be- 'ing ground, the material of which-the chamber siwalls. are composed and other iactors as iswel1 eknown.

:vMany' attemptsf have been made to -eliminate --such1wearor to minimize it as wellaste improve the "effectiveness and: efficiency of the grinding 1; action,: by? employing very hard and tough metal atforzithe.chamber-walls or by surfacing such-walls ;with very hardsmaterial. Other expedients-with :Qthe same-end l in View have been adopted. "some oil these attempts have been partially successful ;.at least to the extent of extending the useful life L of the parts which: otherwise would '.be ;afielcted, ='but-generally speakingg'most attempts have met r fuzith relativeIyindifferent "SUCCESS. In some c p i s, ridge beating ,bars'concussiondiscs h i ik l roie tin irq h chamber nto the pjaths of travel ;of :the'material to g m rqundihavef'been employed but such conj t uctio are-generally;.costlyboth initially and epla'c merit. 'andare-otherwise "objectionherefare alsof those typeset concussion or s iina esl in ;Whi "th ro s,*h mmers or discs are "eguipped' -with friction surfaces "or the likefior special purposes such as shredding ,wood or. other f brous material. However, such machines are generallyunsuitable ior grind- 15';?'i ng or pulverizing-materialssuch as coal or'grain "iand' t-hedike; such-tmaterials usually having to be reduced'to a powder=likeconstituency or condition -under "impact aan'd centrifugal for ces which, ordinarily;-are-not utilized-oronlyutilized to a relativelyssmall extent in pulpy or-fibrous -rna-t'erial'grinding'maphines. Pulverization is sel- 1 dem -possible in such machines.

It is also *desirable;inmachines for pulverizing substanees;- toihave thepulverized material i-."e.,-"the materialwhich has been-reduced to the desired particle size or proper degreeof pulveriza. tion; removed practically as *fast as it has; been .s reduced -to such s-tateandto-=-that end mills of the grinding type-gas '-dist inguished from the --g-rates esigned- 'to- -pass theadequately ground i -fines, as thcy are aferrned iromthe grinding chamber. i-Such' an arrangemenV-may serve to 'srfacil-itate 4 reduction of the remaining unpulverized:pieces and particlesinthe' grinding chama ber-lan'd mayialso permita more =orless continulroussflow :of=. materia1-:to deed -into,- through v and .lrfromathe imachine. In centrifugal or hammer iztypes iOf. grinding mills; -the whirling hammers or! bladeszmayserve toaid in blowing or forcing :the: ground igmaterial ithrough -a screen or grate into rthes disc-harge from the-machine. -'Ma chines SllGh'ifiSiilbhDSG iiemploying rotating friction sur- -faces for: shredding or tearing -material, ordi- V :.nari'1yado: not'zihave. grates orscreens through ewhichr:the-::productiisaxdischarged so do not need writfli have:anyi'ftanitactionrand .such machines are :2generallyv -':of the "cfbatch gatype as distinguished erromezthe:zcontinuoussflew:atype with-which the 5 0 --iirvention= is primarily concerned.

.a'mnong i-the principal-objectsof-j-thejnvention therefore; is that of-providing a:centrif uga1 hammer nrlill type of grinding --machine withla renew- :able ;-0r --rep1aceable "lining composed, of arelatively hard abrasive substance such as silicon be abraded and ground under impact and other.

activating forces induced by the blades or hammers rotating within the chamber. 1

Another principal object isto provide anarrangement whereby a grinding mill of the character indicated may be utilized for a continuous flow of material in feed, in'grinding and in diecharging or, for batch or intermittent feed, grindand discharge, as may be desired. By 1 reason of the high effectiveness and eificiency of a grinding machine of the character indicated when constructed with abrasive linings of the character mentioned and because an accumulation of pulverized product within the grinding chamber would tend to decrease such effectiveness and emciency, it becomes highly desirable, under certain circumstances and when grinding or disintegrating certain materials or substances, to remove the disintegrated or pulverized product substantially as fast as it is formed and it is for that reason that the invention in a preferred application features an arrangement permitting such processing.

Many other objects including the novel processing indicated above, as well as the advantages and uses of the invention will be appreciated and understood by those skilled in the art, after reading the following description and claim and after viewing the drawings in which:

Figure 1 is a side elevation, partly in section, of a presently preferred embodiment of the invention, showing a centrifugal or hammer mill, motor drive and impeller shaft mounting;

Figure 2 is a sectional view in end elevation, taken substantially along the section line 2-2 of Figure l; and I v V Figure 3 is a detail view of a bottom portion of the mill casing looking at the same from a position to the left of Figure 1.

The mill illustrated in the drawings has been more or less conventionalized and generally comprises a cylindrical casing the ends of which may be closed by end plates 5 and 6, plate 5 being provided with an opening for, connection of a supply pipe or chute l and also with a bottom opening closed by a plate 8 for purposes to be described, while end plate 6 is provided with an opening surrounded by a stuffing box 9 through which the impeller shaft H of the mill passes into the grinding chamber. The shaft mounted in bearing blocks 12 supported on a bed I3, is driven by a motor I14 through a coupling l5 and, within the grinding chamber, carries a plurality of firmly secured blades or impellers I6, 16, I6" and "5". The axes of the shaft and grinding chamber are coincident or substantially coincident. Attached to the outer ends of the blades or impellers i6, 16 etc. are beaters; plates or hammers H, which may be formed of any of the usual hard materials employed in mills of this character. The construction of the blades or impellers I8, 46 etc. as well as the type and character of hammers and the other details of construction may be according to any of the usual practices in this art. While II is hammers ll.

the plates or hammers l! are shown as connected to each of three aligned blades or impellers it may be preferred to have a separate hammer or plate for each blade or impeller.

The casing of the mill is suitably supported upon a floor Or other supporting structure and is provided with an opening at its bottom side leading to a discharge conduit I8 in turn lead- 'ing to any place of disposal of the pulverized or ground product. Within the casing over the opening leading to the discharge conduit 18 and held in position thereover by any suitable means. is a removable and replaceable screen i9, this being removable through the opening in the bottom of the casing when the cover plate 8 is removed. The details of construction and arrangement of the screen or grate 18 need not be mentioned here since anyone skilled in the art mayv supply the same. Preferably the screen or grate i9 is arcuate and concentric with the paths of rotation of the blades or impellers and the V Preferably also, the feed pipe or conduit 1 is disposed soas to feed the material to be ground into the grinding chamber at a tangent and against the direction of rotation of the impellers so that the impellers tend to pick up the material to be ground and start it in motion before the material can flow onto the grate or screen at the bottom.

Extending from one side of the bottom or discharge opening in the casing entirely around the inside cylindrical face of the grinding chamber to the opposite side of such discharge opening is a lining generally designated 21 and in this instance composed of a series of individual blocks, bars, slabs or bricks 22 of an abrasive substance such as silicon carbide or anhydrous aluminum oxide. This abrasive lining may be fastened directly to the inner surface of the cylindrical wall 4 or it may be secured in any suitable manner to a generally cylindrical metal liner 23 as shown in drawings hereof, the liner 23 and the abrasive lining 22 being assembled from without the casing and inserted and fitted within the casing from either side when an end wall 5 or 6, as the case may be, is removed therefrom.- The means by which the lining, whether composed of individual bricks or slabs or as more or less one piece structures, is secured to the inner face of the chamber or to the liner 23 is not here material since any method and means commonly employed to secure abrasive blocks or slabs or furnace lining bricks to their supporting structures may be used as will be understood by those skilled in the art. If it is desired, the end cover plates 5 and B may also be lined with an abrasive either in one piece linings'or through the employment of individual abrasive blocks or slabs as will also be understood. i As the shaft and the blades or impellers an hammers are rotated at high speed, the material to be ground is fed down the chute or feed conduit l and entering the grinding chamber is struck by the plates or hammers I1 and the blades or impellers l6, 16, etc. and broken and thrown continuously against the friction surfaces presented by the abrasive linings. Impact blows struck by the whirling parts and by the forceful striking of the lining of the casing by the pieces and particle as they are batted around within the grinding chamber under centrifugal and other forces, quickly reduces the material to a pulverulent condition and the fines, falling upon the screen or grate l9 fall therethrough under the influence of gravity accelerated by the hernill of this in v'erition'Idoes not loperate after the -mannerf crime-usual grinding and crushifnfil'riiills which argely dependent upondragging, sli'afirig and moreor less direct crushing forces to effect disintegration of the material to be broken or pulverized. Instead, this mill effects disintegration and pulverization by throwing the material to be ground, forcefully, again and again, against and along the abrasive surface lining the grinding chamber so that the material is abraded or scratched to pieces by engagement with the hard rasping surface provided by the abrasive. The vanes or impellers whirl the material mass at sufiicient velocity to cause those of its particles which are moved to the mass periphery along the abrasive surface to impinge more or less tangentially upon the abrasive surface and the momentum and inertia of the material pieces or particles cause those pieces or particles to contact a substantial number of abrasive particles in the resultant paths of movement of the material in motion over the abrasive surface, breaking or pulverizing the material by frictional attrition. While there is some breakage and pulverization under impact of the impellers against the material and under impact of the material against the abrasive when whirled thereagainst under high velocity, the impellers do not drag the material between them and the abrasive surface in a shearing or tearing sense nor yet is there a crushing effect after the manner of a jaw-crusher or stamp mill.

Test and experience results have shown that a grinding mill of the instant type has a high emciency per unit of power and is effective to secure a desired degree of pulverization in far less time than may be obtained with other types mentioned. However, effectiveness as well as maximum efficiency of functioning requires an optimum relationship between the quantity discharged and the quantity ground per unit of time. That optimum relationship is a function of several factors but, other factors being equal or controlled, the proportion of total abrasive surface area to the area of the screened discharge opening is, perhaps, the most important. It has been found by tests and experiments mentioned above that the abrasive area of a cylindrical abrasive surface in a machine of the type disclosed herein should be substantially greater than one-half of the total cylindrical surface area and, preferably, greater than two-thirds of the total and up to approximately five-sixths of such total as indicated (by proportion) in the drawing. On the other hand the discharge of ground material must be sufficient to prevent inefiiciency due to clogging and yet must not be so rapid as to reduce the grinding efficiency, but optimum conditions may be obtained, where the screened discharge is under gravity flow plus the blowing effect of the whirling impellers is available, when the screened discharge area is at or between approximately one-fifth and one-third of the total internal cylindrical surface area. In Fig. 2, the screened discharge length in a circumferential direction is illustrated as being somewhat 'less' than onefifth' or approximately one-sixthmf 51131 16 qtotal'cirfzum-ference internally of the, machine. r

Prope'rly chosen and constructed, abrasive linings of the" character indicated will last over saj l'ong period of" time and I are remarkably er- ."fe'c'tive and"eificiei1't in grinding fvery'harfd ma- 3tei=ia1ssuen as 'ores" as 'well' as -relatively.soft Tm'afterialjsuch a'sgrain. Whena lining is iworn'ito fa state where'its efficiency-pr usefulness; is jimpaired, it maybe removed and replaced with a new dining-hubbyutilizing linings of "the types mentioned the grinding emciency and effectiveness remain substantially constant until the linings are completely worn away. When a screen or grate plate is worn or damaged in use, it may be removed and replaced with ease.

The mill constructed after the manner described is eifectively cooled and the material ground therein is maintained at a satisfactory low temperature especially when the material is continuously being fed and the ground material is continuously being discharged and through the fan action effected by the rotating parts. The mill is simple in construction, its cost of repair and maintenance is small and it produces a ground product of uniform fineness quickly and efiiciently. Obviously, the features may be embodied in other forms.

While I have illustrated and described my invention in its presently preferred form, many changes as well as modifications may be made therein without departing from the invention spirit and the scope of the appended claim.

I claim:

In a material grinding machine, a horizontal casing having a cylindrical internal wall, end walls for said casing providing a chamber for the reception of material to be ground, a rotatable shaft projecting into said chamber on an axi co-axial with said chamber axis through one end wall and terminating in the chamber to form an end and the opposite end wall being formed with an opening for feeding material into the casing, said chamber being provided with an outlet opening formed in the lower portion of the cylindrical wall thereof, the area of said opening being not substantially greater than one-sixth of the internal wall area of the horizontal casing, screen means disposed over said opening and conforming in contour to the cylindrical in ternal Wall of said casing, said cylindrical wall being provided with a removable liner having an internal surface of abrasive material, said liner extending circumferentially within the cylindrical casing from one edge of said screened opening to the other and from one end wall to the other end wall, radially extending arms carried by said shaft, material impelling blades carried by said arms, and a feed conduit at one end of the casing extending downwardly and inwardly with its lower end disposed centrally and presented to the end of the rotary shaft for feeding material to the chamber through said opening in the end wall, said feed conduit being angularly displaced with respect to a vertical plane passing through the axis of the shaft and about said shaft in the same direction of rotation thereof a sufiicient distance to feed material to the abrasive surface of said liner in advance of the screen means.

HEINRICH ARNOLD NOLL.

(References on following page) 7 Referenees Cited in the file of this patent Number UNITED STATES PATENTS Name Date Mead Feb. 9, 1886 Barwell Oct. 10, 1916 Adams Feb. 11, 1919 Wood Jan. 1, 1929 Howes Sept. 11, 1934 Banner July 19, 1938 10 Edens Jan. 6, 1942 Egedal May 16, 1950 Number Name Date Harrenstein Feb. 27, 1951 FOREIGN PATENTS Country Date Great Britain of 1906 France Sept. 15, 1922 Great Britain July 26, 1923 Australia of 192'? France Aug. 11, 1936 (Addition to No. 781,736)

Sweden June 3, 1937

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