US1705379A - Mill plate - Google Patents

Description

March I2, 1929. o. SHEPPARD, JR J 1,705,379

MILL PLATE Filed Feb. 1, 1924 s Sheets-Sheet 1 March 12, 1929. o. SHEPPARD, JR

MILL PLATE Filed Feb. 1, 1924 5 Sheets-Sheet 2 a vwemtoz Orlando fhpparq J" flfl'ornu;

o. SHEPPARD, JR

MILL PLA'IE' Filed Feb. 1, 192

5 Sheets-Sheet 3 wue-ntoz Patented Mar, 12, ll929.

entree rattan ORLANDO snnrrnan, Ja, OFATLANTA; GEORGIA.

MILL PLATE.

Application filed February The present invention provides improvements in grinding mills, these improve ments being applicable generally to mills of the kinds employing opposed relatively revoluble grinding plates between the faces of which the material is ground or reduced.

A primary object of the invention is to provide novel and improved grinding plates for attrition mills of the type employing plates having ribs and pockets in their faces between which the material is ground or reduced. l-leretofore it has been proposed to provide the faces of the plates with ribs, some of which extended radially of the axis of the plate and other ribs which extended in a direction generally circumferentially oi the plates, pockets being formed between the ribs, but in the ribbed constructions previously proposed, the circumferential ribs of the opposed plates either produced no grinding action between them or such grinding action as may have been produced between the circumferential ribs occurred only through portions of the relative rotationof the plates, and'hence the capacity of the mill was limited either wholly or largely to the grinding action which occurred between the radial ribs, and furthermore, in such previously proposed constructions, the radial ribs became worn rapidly and also unevenly, thus prematurely rendering the plates unfit for further use. The present invention provides grinding plates for mills of this type wherein the ribs which extend in a direction generally circumferentially of the plates so arranged that they cooperate at all times during the operation or throughout the relative rotation of the plates to produce between them a shearing or grinding action upon the interposed material in course of reduction, these ribs thus co-acting with the radial ribs to afl'ord the maximum grinding efficiency and capacity for a mill. of given size, and, furthermore, the wear will be distributed uniformly be tween the radial and circumferential ribs, so that the period of usefulness of the plates greatly extended. Moreover, the present invention provides aribconstruction which presents two sets of grinding edges, one of -which sets can be brought into use after the other set has become worn or their efliciency has become impaired, it provides plates which may be made in sections which are identical, and hence of equal weight, so that the assembled plates will be inherently 1, 1924-. Serial No. 690,005.

balanced, thus obviating the necessity of providing balance-weights or other balancing means for the plates, and it also provides other improvements in the grinding plates which increase the efiiciency of the mill and obviate objections found to exist in attrition mill plates as heretofore proposed.

Another object of the invention is to pro- I vide a reinforced structure for the grinding plates or members oil attrition mills, disk hullers and snmlar mills where the grinding plates or members revolve at relatively high speeds. Heretofore, it has been usual to make the grinding plates of relatively soft steel or other cast metal, in order to reduce the liability of the plates to fly apart under centrifugal force and thereby damage or wreck the mill,v when the plates become cracked or broken, due to the entrance of a piece of metal or other foreign substance be tween the plates, or to other causes, but in constructing the plates of relatively soft ferred' to, the durability of the plates is accordingly reduced. The present invention provides areinforced structure for such plates whereby the plates may be made of relatively hard cast steel or metal which will afford greatly increased durability and wearing properties for the plates, and the reinforcement will prevent fiyingiapart of the plates, should they become cracked or broken, and, moreover, the reinforcement will retain the broken parts of the plates in proper position so that the-use of the plates can be safely continued until they have served their usual period of usefulness.

To these and other ends, the invention J consists in certain improvements and combinations and arrangements of parts, all as will be hereinafter more fully described, the features of novelty being pointed out particularly in the claims at the end of the specimetal in order tominimize the damage rean enlarged scale,

a section taken radially through a pair of attrition mill plates and their supporting disks constructed as shown in Figures 1 and Figure i represents, on an enlarged scale, a section taken radially through one of the plates constructed as illustrated in Figures 1 to 3, inclusive;

Figure 5 is a detail view of a reinforcement provided by the present invention and applicable to attrition plates and also to the plates of disk hullers other mills, the dot-and-dash line outlining a portion of the mill plate in which the reinforcement is adapted to be embedded Figure 6 represents a section on the 6-6 of Figure 5 illustrating the manner which the reinforcement is embedded in the mill plate; and

Figure 7 is a'diagrammatic view illustrating the preferred mode of generating or laying out the substantially circumferential ribs of the improved plates.

Similar parts are designated by the same reference characters in the several views.

The preferred embodiment of the invention is shown in the accompanying drawings and will be hereinafter described in detail. It is to be understood, however, that the invention is not restricted to the particular construction shown, as equivalent constructions are contemplated and such will be ineluded within the scope of the claims.

In the present instance, 1 designates the disks such as those conmionlyused in attrition mills, these disks being mounted respectively on shafts 2 which may be driven in relatively reverse directions in the usual way,

[the material to be ground or reduced being fed in the usual way between the disks and the material feeding outwardly or toward the periphedcs of the disks under centrifugal force, the material while passing outwardly being ground or reduced between the opposed faces vofthe plates 3, the latter being preferably fitted into recesses 4 formed in the outer marginal portions of the disks and secured therein by a suitable number and arrangement of bolts 5. The plates 8 in the grinding ribs posed plates, throughout the relative rotation of the plates, in consequence of which maximum grinding efficiency and capacity are obtained, the wear takin place is dis tributed uniformly between the circumferential and radial ribs, and other advantages are secured over attrition mill plates as previously proposed. Preferably and as shown in the present instance, the working face of each plate section 3f is formed with an outer peripheral rib 6 which is concentric with the axis of the plate or the disk on which it is mounted, and the working face of each. plate section is provided with a suitable number of ribs 7' which extend in a direction generally circumferentially of the plate but with a pitch toward the outer edge of the plate, and with intervening or connecting ribs 8, which latter extend radially of the plate, pockets or depressions 9 being formed between the radial ribs and the ribs 7 and between the radial ribs and the outer rib 7 and peripheral concentric rib 6. The ribs 7, according to the present invention are so located and arranged on eachplate section that the plate made up of these sect-ions will present these ribs 7 to corresponding ribs on the opposed plate in such a manner that rotation of the opposed plates in reverse directions will produce continuous or uninterrupted shearing'or tion join with or form continuations of the corresponding ribs of the adjacent plate sections. To obtain these results, the ribs 7 preferably extend on arcs of circles, the centers of which are offset relatively to the center of revolution of the plate. Figure 7 illustrates diagramn'iatically one mode of generating the circumferential ribs 7. In this diagram 0 is the center of the inner and outer circles a and 5, while 0 and 0 are centers about which are described the lines 7" and '7" respectively, which lie below and above the line or diameter AB. "By appropriately locating the centers 0 and 0 the arcs 7 which lie below the line'AB will join the arcs 7" which lie above the line AB. Two diagrams conforming with that shown in Figure 7, if reversed and superposed, would present the lines 7 and 7 of the opposed diagrams in such manner that they will not coincide at any point in their circumferences or at any point when relatively rotated, but such lines will always intersect one another at a number of points around the circumferences of the diagrams as the latter are relatively rotated, and if grinding plates were made having circumferential ribs arranged thereonin accordance with the lines 7 and 7" of this dia ram continuousv grinding action would be produced between such circumferential ribs. However, it is desirable in practice to construct each grinding plate of a number of sections and it is also desirable that all sections of the grinding plate be of identical construction in order not only to facilitate manufacture and maintenance by the use of a single pattern and interchangeable plate sections, but also to obtain inherent balance in the plate. It will be found that if the diagram is intersected by the lines or dia'-' meters wrc and 1 so that these lines, to gether with the line AB divide the diagram into six segments of equal circumferential length, the lines 7 and 7" of one dia gram, when superposed upon a duplicate diagram, will intersect on the lines-Al3, m.r and y aI and hence any one of the duplicate segments of the diagram lyingbe tween the lines AB and QJ-% and pattern for a set of plate sections, and a plate made up of such sections would embody circumferential ribs which would produce continuous shearing action throughout the revolution of the opposed plates, and, moreover, the circumferential ribs of any section of the plate would be continuous with the corresponding circumferential ribs of adjacent sections. Preferably and as shown in the present instance, one of the duplicate segments of the diagram lying between the line mw and AB is substantially adopted as a pattern for the circumferential ribs 7 of the plate section, each of these segments constituting one-sixth of the circumference of the diagram and accordingly the'plate is constructed of six sections which will be of identical circumferential rib formation.

In the particular construction shown, 0 is the approximate center of the circumferential ribs of each of the respective plate sections as these ribs are shown in 2, it being understood that the centers of the circumferential ribs of each plate section are nearly or substantially coincident, and

that the centers of the ribs of the different plate sections are located in eccentric relation to, and are spaced eccentrically around, the center 0 about which the plate revolves. ,Each of these circumferential ribs is preferably an arc of a true circle with its center ,so located that each of such ribs extends from a point within the periphery of the plate section outwardly toward the periphery thereof and so that each continuous circumferential rib of the plate extends-from the inner edge of the working face of the plate continuously through the different sections to the peripheral portion of the plate, the ends of the circumferential ribs of any one section alining with or forming continuations of the corresponding ribs of the adjacent plate sections. Of course,

there will be six sets of these rib centers located around the center 0, in the construction herein shown, to conform with the use-of six circumferentially extending but outwardly-pitched ribs. It will be'understood, however, that any equivalent arrangement of the circumferential ribs which will produce continuous grinding action upon the inaterial between the plates throughout their revolution maybe used, although 7 it is'also desirable that the circumferential ribs of one plate section should be continucircumferential rib are substantially perpendicular to the'plane of the working face It will also of the plate to provide efficient cutting edges on the inner and outer sides of each of these ribs, so that when one edge of the circumferential ribs of each plate has become worn, the mill disks carrying the plates may be reversed and the operation of the mill then be continued, bringing'theouter edges of the circumferential ribs of the opposed plates into operation. In this way, greatly increased serviceability of the grinding plates is obtained. In order to facilitate the passage of the material undergoing reduction between the working faces of the plates and also to avoid banking or packing of the material against the inner walls of the circumferential ribs and thereby disturbing the balance of the plates, a fillet 7 is preferably formed at the inner sideof each circumferential rib between its face and the body of the plate, but this fillet terminates short ofthe workingfa'ce of the r1b,-thus leaving an effieient cutting edge at the inner side of the rib, similar to the cutting edge at the outer side of such rib. The sides of the radial ribs 8, as shown, are preferably substantially perpendicular tothe plane of the working face of the plate,

so that these ribs present efiicient cutting edges at both sides thereof. Thecircumferential ribs 7 and the radial ribs 8 preferably reduction, but the working faces of the ribs. from the inner edges of the plates outwardly to the line LL are preferably beveled slightly so that they converge as they approach the line L.L, this bevel of the working faces of the ribs facilitating the feeding of the material between the plates and thus promoting the grinding action. The inner edge of each plate is also preferably formed with a beveled feeding surface 10 and a suitable number of breaker ribs 11 are preferably provided which project forward from the feeding surface 10, these breaker ribs serving to break up the material which may be fed to the plates in the form of cakes or lumps, thereby facilitating the entrance of the material between the working faces of the plates. I

In using a pair of plates each constructed substantially as hereinbefore described, the plates, when placed opposite to one another will present the ribs 7 to one another in such relation that they will always intersect at a number of points throughout the relative rotation of the plates, the ribs 7 avoiding coincident superposition at any point, and

'in the operation of this mill, during which the plates are relatively, rotated, it being usual to revolve both plates but in opposite directions, the ribs 7 ofthe opposed plates will produce and maintain a continuous shearing action between them and also between these ribs 7 of each plate and the radial ribs 8 of the opposed plates, Figure 2 showing clearly the shearing relation be-' tween the ribs 7 of the opposed plates. In consequence, maximum grinding efliciency and capacity are attained and the wear of the plates is distributed uniformly between the circular or circumferential ribs 7 and the radial ribs 8 so that the working faces of the plates are maintained in efficient working condition for a maXimum period of time.

The present invention also provides means for reinforcing attrition mill plates and also the plates of disk hullers or other mills which are subjected to centrifugal and other strains while in operation and which, if broken in consequence of the entrance of a foreign body between the plates, or from other causes, would fly apart and damage or Wreck the mill or the entire set of plate sections in the mill. Heretofore, the strength and durability of grinding plates have depended upon the kind or quality of raw material from which they were made and the v their period of usefulness, and if hard enough to sustain wear for a longer period would be brittle, and hence subject to breakage and destruction. Difficulties in obtaining castings of uniform quality of hardness have resulted in the production of mill plates, some of which were too soft to sustain wear for a sutlicient period of time and others were too hard and hence were subject to breakage and destruction.

The present invention provides a reinforcement adapted to be embodied in a mill plate or the sections thereof and capable of greatly strengthening the same so that it will greatly resist breakage and if breakage of the plate or plate section should occur, the reinforcement will serve to retain the fragments or broken parts of the plate or plate section in proper position, thus not only avoiding damage to or destruction of the mill, but also enabling the operation of the mill to con inue until the plates have served their usual period of usefulness.

In the present instance, a reinforcement is f shown which suitable for use in attrition mill and disk huller plates, the reinforcement comprising a mesh composed of a suitable number and arrangement of bars 12 and 13 of tough steel or other suitable material capable of withstanding breakage, either or both of these rods at their intersections being preferably offset, as at 14, to produce a fastening or interlocking engagement be tween them. This mesh is embedded in the mill plate or mill plate section by casting the steel or metal composing the plate around the reinforcement, so that the reinforcement lies in a plane about midway of the thickness of the plate and in the plane of rotation thereof. Preferably and shown in the present instance, the rod 18 in. the middle of the plate section extends radially thereto and the other rods 13 are suitably spaced in parallelism with the middle rod, these rods adjacent to the plate-securing bolts 5 being preferably spaced more closely than at other parts of the plate section in order tosecure greater reinforcement of the plate section in the regions of the securing bolts. The reinforcement bars 12, as shown in the present instance, intersect the bars 18 at or substantially at right angles and they are suitably spaced between the inner and outer edges of the )late section.

In using a rein orcement substantially as herein shown and described, the grinding plate may be composed of a steel or material much harder than it has heretofore been possible to use with safety, so that the grind greatly strengthens the plate so that'itis" capable or P88153111, 'to a high degree, forces weak it, and tthe plate ing plate will possess ear-resisting proper-i ties to a high degr e, and hence the useful 'ness of the plate ivill be-greatly prolonged.

The. reinforcern ht which isen'veloped by the steel or rnaterlal composing the grind ng plate and 11s nitiu'nately unlted therewith,

tendin .orrackor should become broken, the reinforcement will hold the fragments or parts of the plate or plate section in proper position, thereby Y not only avoiding damage to the mill, but 1 alsoenabhng the operation of the null to {section until the plate, a period oi usciulness,

continue, using" the brokenplate oi plate has jserved its usual I The preferred to in of ribs on the workjng faces of the plates has been heretofore) described whereby continuous shearing ac-7 r ionon the .niaterial undergoing reduction will. be produced, throughout the relative revolution ofthe plates, between'the genlly circumierentially eitending' u ward, 1y" pitched .ribsof' the opposed plates, and

between the generally circuniferentially eX- grinding efiicienoy and" increased capacity for' a hull of given sizeybut itsisto be; un-

derstood thatother or equivalent rib formations inay be used toobtain substantially the It is preferable, however, to

smile results; v form the generally'circurnferentially extending ribs as "arcs of true circles having .a pitch from the inner toward the. outer edge o ftlie plates, substantially as herein shown,

and to'construct each plate of a pli'irality of' identical segmental sections so that the ends of, the circuin ferentially extending ribs-of any section aline or are continuousvvith the I er ivear' resisting' .properties than' it.-h'as been; heretofore? safe "to use, for. notw'itlr standing the liability fof b'r'je'akageuofsuch circumferentialcribs' of adjacent sections,

I {the manufacture of theplates'beingthusfa c'ilitated, the plates being inherently loal ancedfandundue ear 0 grooving of'the radial ribs being avoided; It-is' al so pref- 'l e o for the ircum erent y en ing eutivardly pitched ribs with right "an led or efficiently-shaped inner and outer cuttiiigeclges whereby the period ofus'eful nessof'the plates may be increased by reversing the mill disks carrying the plates,

after one pair of the cutting edges provided by these ribs has become Worn, thus br nging ,7 the other set of cutting edges into; operation.: The fillets at the inner sides ofthel circiunferenti allyextending ribs are preferably used as theyfacilitate the outward- 1 feed of the 'niateri'al undergoing reduction and they also avoid banking of the material" againsttheiinner sides ofthese ribs and which, it allowed to occur, lvv ould unbalance fl llflp l l Y I Preferab ly, and as shown in the present instance, one o'f' the-circumferential ribs commences on" each of the plate sections,- these ribs extendlng around the face of the' plate so that the portions of these ribsborne each plate section are ali'nedf. this dentical circumferential rib formation all of the sections and the sections Will be entially by'portions of; other ribs; "Inthe particular construction shoivnyflthe circun1- ieren'tial ribs are also located; symmetrically on-the' working face of the plate,tll1e centers of these ribs being 7' located, eccen trically of and spaced symmetrically around the axis of rotation of the plate,f and hence hcrentlybalanced, the number ofjcircuin .ierential ribs correspondingkvfih the nuni-f ber of plate sections used, and each circum-- :lferentialrib will be overlapped circumfen "angeniont, each plate section ill have an I ,"thereon, so that one pattern will serve for thcdifferent circumferential ribs'vvillstalrt at points s g innerport 1 of thei Workingfface otjgthe plate "and \v1ll tern"11 nate' at polnts spaced such f ribsn I I I ng functron here n descr bed, but theymay also cedsymmetrically around the 7 V p 00 *syinn et ically *around 'fthe outer portion of V c. g course, the circurnferentlal Y c only perforintheshearing or grind ter-ial priorto itsfinal'dis'charge attheperiphery of th'e plates. V i r 1 i The reinforcement provided by, the" present invention enables thef' grindingfplates I of. mills" oi'fflvarlous tfy'z p'es or l'rinds to; be

constructed or hardenmaterialfand of great plates, due to the increased; 'hardness flof -theanaterial=coinposjinglthem,the reinforce-j 3, .nient not only resists; forces tending to break plates,- but j should se'ctiongf oii'ieither r xpiate be'coniej' broken, its parts will beheld together and in proper working position, so

thattheoperation of? the mill'inay be safely continued,- the broken plate section operating substantially as if unbroken. The preferred form of the reinforcement as applied to attrition' inill platesis herein shown and-def; I scribed, but it is to beunderstoodthat the I V reinforcement may take other forms in plying it tothe grinding plates of attrition inills," disk hullers or to the grinding plates of mills of other types; Obviously, if'the j. mill plate, to which} thereinforcernent is] ap'plied is const-ructjed v in"one pie'ceinsteadl of in segments, the forlrn oi? tl 1 e rein; 1130s iforcement maybe vari'ed to I conform there 'with.

I, claim as my'invention A grinding plate for mills having a fw'orking 'face provided with a set of pro-- je'cting' ribs which extend circumferentially [of the plate, the inner side 'ofeach rib hav- Ling a portion. extending substantially per- ,pendicularly to and forming a cutting edge with the face or the rib, and a fillet oining thel face of the plate with said portion of the inner side of the rib at a point removed I n from, saidc'uttin'g edge. I

} QXA reversible grinding plate for millshaving a working face provided with a set 7 of projecting ribs, which extend circumferentially and are pitched outwardly from vpoints toward the inner side to points to- I ward the outer perlphery of the plate, the

inner side of each rib having portion extending atl an angle to the face of the plate to form, a cutting edge with the face of the ,rib, and a tilletjoining theface of the plate .removed from said cutting taining fragments, broken from the plate,

in' working position.

Q 4. A grinding plate for mills comprising a body of hard cast steel'havingva dressed working face and a tough steel rod :r'einforcement embedded in the body behind said i dressed face and intimately united there-* witlrand operative to maintain fragments,

c T broken fro1n- ,the p late,- in working position.

A;- gr'1nding;plate;;comprising a body-M r I I stresses towhlch the plate is sub' ected. while in "operat on to maintain fragments I of 'a composed fofhard cast steel having a dressed working face and a strain sustaining -rein forcement 1 composed of tough steel embed d'ed inthe'body in aflplanebehind its work- --{ing face; said reinforcementbeing intimate- I 1y united with the hard cast steel composing a the body. and operative to maintain frag- -op eration.

ments, broken from the platefin'working position.

6. A grinding plate comprising body of hard cast steel having a dressed "working face and an intersecting rod reinforcement composed of tough" steel-embedded insaid bodyand intimately united'therewith, said reinforcement constituting a strain-sustaining structure capable of maintainingfragments of a broken plate'in working position. 1"

7. A grinding plate comprising a body of hard cast steel having a dressed working face and a tough: steel reinforcement embedment embodying. sets'of intersecting menibers, the members of one set-being recessed to-engage andinterlock with thef members of the'othcr set, thereinforcement being opded in the bodybehind saidd'ressed face and llllilll'lttelyilnll ttl illlQIGWlill,StLl(l TGHIfOICtF g its face and'coinposed, ofa hardsteel cast-c ing which alone is too brittle to preclude fracture under the stresses tdwhich such plates; are sub ected' n service, and a reinfor'cement about which said body is cast and intimately united therewith, said reinforceni'entfbeing' operative to maintain fragments,

during operation. V v p 9. An attrit1on-m1ll 'plate comprising a broken from the plate,in working position "body composedof a hard steel casting of in sufficientresistance alone to preclude frac-- t'ure under the.stresses to which such plates are sub ected in service andhaving a'r-ibbed working face, and a tough steel reinforce ment .about'which said body is cast and with which it is intimately united, saidreiiiforce ment lying} infa pla11e- 'behind said ribbed working face, and belng. operative to-sustain fracturedplate inworkingrelation during or g 95, 7 In testimony whereof I have hereunto set i r OBLANDOSHEP-PABD, JR, 5;

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