US2893650A - Grinding mill end liners - Google Patents

Description

y 7, 1959 N. E. MACLEAN 2,893,650

GRINDING MILL END LINERS Filed 001:. a, 1957 3 Sheets-Sheet 1- Norman E Ma clean.

N. E. MACLEAN GRINDING MILL END LINERS July 7, 1959 3 Sheets-Sheet 2 Filed Oct. 8, 1957 Inventor .Norman. E. Maclean w g/4; Md am q-l-lornags y 7, 1959 N. E. MACLEAN 2,893,650

GRINDING MILL END LINERS Filed Oct. 8, 1957 3 Sheets-Sheet 3 Inventor Norman Maclecm.

5 Mal/aw and 3 fi'l'fliorney United States Patent GRINDING MILL END Norman Maclean, San Marino,- Califi, assignor to American Brake Shoe Company, New York, N.Y., a corporation of Delaware Application October 8, 1957, Serial No. 688,968

' 3 Claims. (Cl. 241-181) This invention relates to an end liner for a grinding mill.

A common method of comminuting relatively large particle size material such as are is to char e the material into a rotary grinding mill to be subjected to the action otgrinding media such as cast ferrous metal balls, mineral-type balls or the like. The mill includes a shell supported for rotation about a horizontal axis and is provided with verticalend walls which confine the charge; It is common practice to line both the shell and the end walls with liners of wear resistant alloy exposed directly to the abrading' action of the charge and the media-so as" to protect the shell and the walls of the mill againstdirect wear.

The end liner for a mill is relatively expensive, and when wdrn out it is necessary to shutdown" the milr and replace the worn liner. It is therefore advantageous to reduce Wear on the end liner itself, and the accomplishment of this in a novel manner is a primary ohj'ect. ofthe present invention. v

Specifically, it is the objectof; the present invention to provide the end' liner of agrinding or' s'o c'z'tlled ball mill with a rib that projects outwardly from the wear serrate thereof and whieh extends at an aiigle to the radius of the end liner. This angle willbe an acute angle, that is', subsrefiaany less than normal to the radius wherehy th has a leading end which in eiiec t accounts f r a'seeo fig action on the rinding media, reduein endl-inef wear a noiel manner that will be eXplained detail herein anew: The p'r'es'ent invention is,- t'herefore', to be distiiigiiisliedfrom end liners as heretofore constrticte'c l haviiig truly radial ribs, and is' arseto be distilFg'tii'sh'ed f or'n end liner having a rih whiehis tangent to a radius of end' liner. p the art, an end lifief tor a grind iiig rhill may he advantageously constiiuefed in the forhi of at segment. Anend near or this term is asseinmed with the requisite num er of like segments to afiord a eemptete- 3'60 plate or dise assembly. Such an end liner may he as large as I80", or smaller, such as on the order of 30, an when worn' is readilyreplaeea'ble in the 360 assembly. In other instances, the eiid liner may be cast as a one-precast) part. In any event, either the segment assembly" or the one=piece eons'truction is com"- plerrierital to' the area of the end wall. of the mill;

' Where the construction is to include a: plurahty of end liiiers assembled in a 360* pattern in the foregoing manner, theindividualsegments. of the present invention can be successively cast one by one; in a single mold, and tinder the present inventioneach such segment will be formed with a rib", whereby in: the assembly of segments the. ribs have a pin-wheel appearance. This appearance will also occur, of course, where the end liner is cast as a one-piece 360 part, and the assembly iiv'itliinv the mill is siieh that the non-radial, non-tangential rihs have" the oiiter ends thereof pointing in thedirection of mill rotatio'fi the ends of the ribs in trailiiig position.

Mills of the foregoing kind may be either of the sofit) ' in'g media on the end liner.

, "2,893,650 Patented July- 7, 1959 called high or dry discharge type, or of the'so-called low or wet discharge type. In the latter type of mill, the charge is mixed with liquid which carries the comminuted fines out the discharge opening atthe discharge en'd of th'e mill, and a grate or screen is located in front of the discharge'opening so asto clarify the fines prior to discharge; Such a grate or screen is also known-in the art as an end liner, because it islocated infront of the discharge open ing at the end of the mill so as to take the Wear and is cast of wear resistant alloy. It is also common practice to construct the end liner screen or grate as an assembly of liners of segmental forr'n heldin place within the-mill by wedge bars or the like. The present invention" is ap' plicable to both types of end liners, that is, the solid or non-foraminous type for a dry mill and open or screentype for a wet mill.

It is recognized that it is' not new to form a rib on an end liner of a grinding mill so as to project inwardly from the wear surface of the liner. However, the common practice in the past has been to construct the ribs of truly radial form, that is, disposed normal to the direction of mill rotation. It was apparently intended that theribs thus disposed would sweep through the grinding media in some manner to reduce the abrading action of thegrind- Aswill be explained herein below, radial ribs do not induce-the desirable action of the grinding media that is induced by a ribon an end liner" constructed in accordance with the present invention. It is, therefore, a further object of the present invention to reduce wear on an end liner by' resorting to a rib which is so angled as toencoiirage the intended action of the grinding media. I

Other and further objects of the present invention be apparent from the following description and claims and are illustrated in theaccompanyingdrawings which; by way of illustration, show preferred embodiments of the present invention and the prineiples thereof andwhat is now considered to be the host mode centempl'atedrer applying these principles. Other embodiments of the invention embodying the same or equivalent princ'iplesni'ay be used and structural changes may he made as desired by those skilled inthe art Without departing from the present invention and the purviewof theappendedelaimsl In the drawings:

Fig. l is a perspective view ofa mill constructed inaccordance with the present" invention, the; shell Benig broken away toexpose the end liner at one end of the mill; Fig. 2 is a perspective view somewhat similar to' Fig. l but further illhstra'ting normal action within the mill-';'

Fig. 3 is a section through the shell' of the mill and illustrating action of the grinding mediain the central area thereof; V n

Fig. 4 is a fragmentary view on an enlarged scale illll-Sf trating in detail the normal grindingaction of grinding media in the mill; M 4 i Fig, 5 is a fragmentary view illustrating movement of the grinding media atthe end of a conventional mill during ro'tation of the shell; p

Fig. 6 is a fragmentary view similar to Fig. 5 but showing the conditions prevailing. at the, end of a having an end liner with aradial rlb'; p l

Fig. 7 is a plan View of a 360 assembly of end liners constructed in accordance with the present invention;'

Fig. 8 is an elevation of two segment end liners of the present invention and the novel action imparted to the grinding media thereby;

Fig. 9 is a partial plan view of end lir'ier' segments constructed in accordance With the present invention; v

Fig. 9A is a sectional view taken substantially'en the Fig. 10 is a plan view of an end liner for a wet mill constructed in accordance with the present invention; and

Fig. A is a sectional view taken substantially on the line IDA-10A of Fig. 10.

In Figs. 1 and 2 of the drawings there is illustrated a dry 'or so-called high discharge grinding mill 2!) of the kind used to comminute to a finer state ore material M, Fig. 4, charged into the internal chamber 21 thereof. The mill 20 thus includes a conventional drum or shell 25 of cylindrical form disposed to rotate about a horizontal axis. The inner face or wall of the shell may be provided with removable liners (not shown), and secured to the opposed ends of the shell 25 are heads or end walls 27 and 28, Figs. 1 and 2. Associated with each end Wall as 27 and 28 is a trunnion as 33 and 34. These trunnions are coaxial with the axis of the shell and are respectively supported for rotation with the mill in respective bearing blocks 31 and 32 which are a part of heavy duty standards 35 and 36 which carry the entire load of the mill. For rotating the mill, a ring gear 39 is secured to one of the end walls, and this gear is adapted to be driven in a conventional manner by a pinion gear at the end of a drive shaft (not shown).

The end walls 27 and 28, as well as the end liners associated therewith and to be described hereinafter, are respectively formed with feed and discharge apertures at the centers thereof. The trunnions referred to above are in the nature of sleeves, and the inner ends thereof communicate with the apertures in the end walls and the end liners. Accordingly, the trunnion as 33 at what constitutes the feed end of the mill enables the mill to be charged with the material to be ground or pulverized as well as with the grinding media. Likewise, the trunnion 34 associated with the end wall 28 affords the discharge.

Both the feed and discharge openings in the end walls and the end liners communicate with the chamber 21. The heads 27 and 28 of the mill '20 are provided with end liners 40 and 41, Fig. 2, of novel construction to be described hereinafter. The liners 40 and 41 are in the form of one-piece castings, but the end liners may be of different forms as will be described. Moreover, the end liner for the discharge end of a wet mill is of further modified form as will be described.

End liners as 40 and 41 for a dry mill, Fig. 1, will in most instances be of identical construction, and it will be noted that these are in the form of relatively large discs or plates each adapted to be disposed in a vertical plane inwardly of and parallel to the associated head or end wall 27 and 28. In the dry mill form of the invention, the end liners are anchored to the end walls for rotation therewith, usually by nuts and bolts. For this purpose, the liners 40 and 41 are formed with apertures 43, Fig. 1. The direction of rotation has been indicated by the arrow R as a reference throughout. Each liner includes a fiat, smooth wear surface as 40WS, and when vertically oriented the wear surfaces 40WS face inwardly of the mill chamber 21.

Thus, the liners 40 and 41 serve the known purpose of eliminating direct Wear of the grinding media on the inner faces of the end walls 27 and 28 of the mill. Consequently, it is the wear surface 40WS of the end liner which is subjected to the abrading action of the grinding media such as ferrous metal balls B so as to take the wear at the ends of the mill. Each end liner 40 and 41 includes an arcuate outer peripheral edge 46, Fig. 2, and an arcuate inner peripheral edge 47, Fig. 1, these edges lying on true concentric circles. The inner peripheral edge 47 is substantially colinear with the diameter of the discharge opening at the discharge end of the mill, or substantially colinear with the feed opening at the feed end of the mill as the case may be. Where the feed and the discharge openings are of difierent internal diameter or configuration, the aperture 47 of the end liners 40 and 41 will of course differ to this degree.

Likewise, the outer peripheral edges 46 of the end liners 40 and 41 are substantially colinear with the inner diameter of the shell 25 so as to engage the inner diameter of the shell 25 about the circumference thereof corresponding to the related end liner, and it may be mentioned at this point that the shell or drum 25 is illustrated in an unlined form, although, as will be appreciated, it is conventional practice to line the inner diameter of the shell 25 to eliminate direct wear thereon. If so lined, the end and the shell liners will be so related as to present a substantially complete internal lining for the mill.

In accordance with the present invention, in the embodiment shown in Figs. 1 and 2, each end liner 40 and 41 is formed with a plurality of ribs 50 which are arcuate in form and which extend from the inner peripheral edge 47 to the outer peripheral edge 46 of the end liner. The ribs 59 are non-radial, that is, are disposed at an acute angle to a radius line joining the inner and outer edges of the end liner and intersecting the rib 50. The appearance is one of a pin-wheel whether the ribs be arcuate as shown in Figs. 1 and 2 or straight. The ribs all have substantially smooth surfaces and may have any desired configuration in cross section. Preferably the ribs project from the wear surface of the end liner an axial distance approximately equal to the radius of the grinding balls B used in the mill, but this dimension is not critical and can be varied for different circumstances.

As mentioned above, the end liners 40 and 41 are onepiece castings. This is merely illustrative of one type of commercial installation. In most instances, however, it is preferred that the mill be lined at the end thereof with a plurality of segments of pre-determined segment angles which, when assembled, line the end walls of the mill for 360". Thus, referring to Figs. 7 and 8, end segment liners 55 are afiorded for lining the end of-the mill 20. Each of the end liners 55 has an inner peripheral edge 57 and an outer peripheral edge 58 lying respectively on corresponding concentric circles which, it will be appreciated, correspond respectively to the feed or discharge opening of the mill, and the inner diameter of the shell 25 of the mill. Each end liner 55 likewise has an inner wear surface SSWS which faces inwardly of the mill. In view of the segmental nature of the end liners 55, these are case or otherwise formed with portions of the non-radial ribs, which portions, in the 360 segment assembly, have aligned ends which complete the extension of a rib from the inner peripheral edge of one end liner to the outer peripheral edge of the next adjacent end liner.

Thus, referring to Figs. 7 and 8, a particular end liner as 55-1 is provided at the radial outer section thereof with a rib section 60A1 and is provided at the radial inner portion thereof with a rib section 60131, both rib sections being arcuate in the form illustrated and acutely angled relative to the radius line drawn from the medial point on the inner edge 57 to the medial point on the outer edge 58. Using as a reference the direction of rotation R in Figs. 7 and 8, the next leading end liner 55-2 is formed with spaced ribs 60A2 and 60B2 which are identical in configuration, spacing and disposition to the ribs 60A1 and 60B1 of the trailing end liner 55-1. The rib portion 60B1 extends from the inner trailing edge corner TC of its end liner to the medial point M1 of the leading side edge of the end liner 55-1. The rib portion 60A2 of the end liner 55-2 extends from the medial point M-2 on the trailling side edge of the end liner 55-2 to the outer leading edge corner LC thereof. The relative disposition of the end liners 55-1 and 55-2 has been altered in Figs. 7 and 8 for reasons apparent in the description to follow having to do with the novel effect of the ribs on the grinding balls B, Fig. 8. It may be further mentioned that the leading and trailing side edges of the assembled end liners, Fig. 7, are spaced one from another at S, and are usually bevelled to enable complemental wedge bars to be mounted in the radial spaces S to clamp the liners 55 together, these wedge bars. being turnbolted to the end walls of the mill, all in amanner well knownin the-art.

'Ifhe'novel eifects achieved by. the end liii'er constructed in accordanee with the present. invention. can be bestexplained with reference to Figs. 3 to 6 add 8 ofv the drawing. Normally, a grinding mill is filled about half full with grinding media such as the balls B, andwhen rotating, centrifugalforce throwsthe mass ofgrinding media. to. one side of the shell as indicated in Fig. 3. The grinding media mass is. thus subjected to gravitational influences, and. the balls at the top of the mass tumble down an incline L- as. indicated in' Figs. 2 and 3 This tumblir'ig representsone of the phenomena accounting for some comminut ion'. of the matcri al being acted upon by the grinding balls in the mill. The balls B are considerably larger than the size of the ore material fed into the mill for grinding, and roll over the ore in accomplishing comminution; This is: particularly pronounced the centralv re'gi'cin CR, Fig. 3, of the. grinding .media mass. This particular phenomenon can be best appreciated by referring to Fig. 4 wherein the balls B' rotate about. their own. axes due to the impulse directed. to the balls which are in coritact with; the shell 25, and the balls B that are thusset in rotation directly grind between them the ore material M. -It is therefore essential that the. balls rotate on their own axes independently of rotation of the shell of the mill, since theoretically, if the balls do not. fall,

. takes theform of assembledsegments. 'I'hus,; referring to Figs. 9 and 9A, which show one form of the invention for commercial installation two series of v ribs are used, a series of long ribs and a series of short ribs. Each long rib 70 extends from a point spaced. slightly inwardly of the inner edge 71. of the end liner to a point no grinding would be accomplished except what might be accomplished due tothe tumbling action down the incline L.

Considering now the acfioniat .theiendfwalls of the mill, and referring to Figs. 5, 6 and 8, it has been known for a long time that the balls in contact with the end liner EL, Fig. of the'mill donut partake of the rotary motion of the ballsv at the center of the mill as described above. The balls at the end of the mill, Fig. 5, at best slide baclwards relative to the wear surface of the. end liner without partaking of individual rotation, and accordingly grinding actidii at the end of the mill, and for almost a foot inwardly from end of the mill, is reduced to a minimum. This I believe is due to the frictional resistance of the wear surface of the end liner to the axial outward pressure or crowding effect exerted by the mass of balls B against the wear surface of the end liner. Moreover, the balls B, Fig. 5, sliding in contact with the end liner EL produce a great deal of wear on the end liner, and accordingly it has been proposed to install in the mill a modified end liner EL, Fig. 6, having a rib RN of truly radial form projecting from the wear surface thereof. The rib as RN acts as a back-stop preventing back-sliding of the balls and serving to in effect push the balls bearing against the end liner EL around with the shell 25. In this manner, it has been proposed to reduce wear on the end liner EL. It will be recognized, however, that the rib RN at best reduces wear on the end liner, and the phenomenon, of whatever origin, which prevents individual rotation of the balls B in Fig. 5, and for a substantial distance inwardly of the mill, also prevents individual rotation of the balls B in Fig. 6. In other words, even with an installation of the kind shown in Fig. 6 grinding action at and adjacent the end of the mill is reduced to a minimum, and under the present invention grinding action at and adjacent the end of the mill is enhanced as will now be explained.

Thus, and referring in particular to Fig. 8, the ribs of the end liner of the present invention are non-radial and are angled so that the outer ends thereof adjacent the outer circumference of the end liner are in a leading position while the inner ends of the ribs are in a trailing position. Accordingly, the ribs on the end liners of the present invention have a scooping action on the balls which imparts individual rotation to the balls bearing against the end liner. The ribs of the present in on the leading side edge LE of the and liner somewhat inwardly ofthe leading, corner of the endliner. The outer end portion of the rib 70 istruncated, and the remaining terminal portion 70A thereof is castv at the medi ately opposite pointat the trailing side edge TE of the next leading one of the end liners. r j

The shorter rib 75 is disposed in trailing position rela tive to the rib 70, the direction of rotation of the mill beingagain indicated at R. in Fig. 9. The short rib'for the end liner has its outer or leading end lying on a circle that is. common to the outer ends of the .long and the short ribs. The rib 75 extends inwardly of the end liner approximately parallel to the rib 70 and terminates at a point on the trailing sideedgeof the end liner. The inner end portion of the rib 75 is truncated and the supplementary end 75A is cast at the immediately opposite ppinton the leading. side edge of the next trailing end liner. An endliner ofthe kind, shown inFig. 9 has,- of course, a wear surface WS, and the ribs are formedon 1 this surface so as to bel inclined at an acute angle to the radius line joining r'nedial points on the inner and outer edges7j7- and 78 of the end liner which lie omc'oncent ric circles as in theforegoing embodiments.

The present invention may also be utilized. in a screed type. end-liner for a wet mill as shown. in Figs 10 and 10A. Thus the screen or grate-type liner Sll showh in Fig. 10 is formed with the usual classifying openings 81 through which the fines produced in the mill are adapted to pass from the wear side WS, Fig. 10A, to the discharge side D8 of the end liner. The discharge side D8 of the end liner will face the rather narrow discharge space aiforded between the end liner 80 and the related end wall of the mill, this being a well know-n arrangement and hence not illustrated.

The end liner 80 is cast in this instance with entire ribs 85 and 86 in contrast to the modifications described above wherein adjacent end liners were cast with supplementary parts or sections of the ribs. As in the foregoing embodiments, the ribs 85 and 86 are cast to extend at an acute angle relative to a radius line joining medial points on the inner and outer peripheral edges 87 and 89 respectively of the end liner 80. Both ribs 85 and 86 are straight rather than arcuate. The rib 85 is the longer as well as the inwardly disposed of the two ribs, and extends from what constitutes the leading corner of the grate-type end liner 80 to a point on the trailing side edge of the end liner 80 spaced outwardly of the inner peripheral edge 87 of the end liner 80'. The shorter rib 86 extends from a point on the trailing side edge of the end liner 80 to a point on the outer peripheral edge 89 of the end liner 80. The general disposition of the end liner 80, and as many like segments as are required to complete the 360 assembly of end liner means in the mill, is the same as what has been described above. Thus, the edges 87 and 89 have points lying on concentric circles, and these circles will correspond to the inner end of the discharge opening (of the wet mill in this instance) and the inner diameter of the shell.

It will be seen from the foregoing that under the present invention there is afforded an end liner for a grinding mill having a rib of novel form formed on the wear surface thereof and which projects therefrom in an axial direction so as to project inwardly toward the chamber of the mill on the. same side as the wear surface. Usually the end liner will be cast, either as a one-piece complete 360 plate, or a segment plate of predetermined segment angle having what constitutes leading and trailing side edges which are actually true radii and hence diverge outwardly. Whether a one-piece 360 plate or an assembly of plates, the end liner means operatively associated with the mill, whether wet or dry, will be anchored to a rotating part of the mill so as to rotate with the mill; and the inner and outer edges of the end liner plate will lie at least on points of concentric circles. In nearly every instance, these circles will be actually substantially colinear with the inner diameter of the mill shell, and the inner end of the feed or discharge opening of the mill as the case may be, within reasonable tolerances in casting and mechanical mounting. If the end liner is a sufficient- 1y small segment, the inner and outer edges thereof conceivably could be straight, rather than arcuate as shown, especially where so to do effectively lines the end wall of the mill.

Hence, while I have illustrated and described preferred embodiments of my invention it is to be understood that these are capable of variation and modification, and I therefore do not wish to be limited to the precise details set forth, but desire to avail myself of such changes and alterations as fall within the purview of the following claims.

I claim:

1. In rotary grinding mill apparatus of the kind de scribed having a substantially cylindrical shell mounted for rotation about a substantially horizontal axis, and afiording a chamber in which the grinding media and the charge to be comminuted are to be confined, end liner means arranged at one end of the shell in a substantially vertical plane for rotation with the shell, said end liner means being in the form of a plurality of identical segments extended for 360 about the end of said shell and .eachhaving a wear surface facing inwardly of said chamber so as to be subjected to the action of the grinding media in said chamber, said end liner segments each having inner and outer peripheral edges lying substantially on respective circles extending substantially concentric to the axis of rotation of the mill, and at least a pair of ribs formed on the wear surfaces of each of said segments, one being an outer rib and the other being an inner rib, each of said ribs on a segment being inclined at an acute angle relative to the correspending radius line of the segment, theouter rib having an outer end disposed near the outer peripheral edge of its segment in a leading position and having an inner end disposed .at a point along one side edge of the segment in a trailing position, the inner rib having an outer end disposed at a point along the other side edge of the segment in a leading position and having an inner end disposed near the inner peripheral edge of the segment in a trailing position whereby each of said ribs in travelling through the grinding media at the end of said chamber impedes back-sliding of the grinding media against said wear surface and imparts rotation to the grinding media about their own axes.

2. Apparatus according to claim 1 wherein the inner end of the outer rib of one segment is aligned with an extension on the next segment.

3. Apparatus according to claim 1 wherein the inner end of the outer rib on one segment is aligned with the outer end of the inner rib on the next segment.

References Cited in the file of this patent UNITED STATES PATENTS 1,381,987 Gordon et al. June 21, 1921 1,589,740 Bonnot et al June 22, 1926 1,744,089 Williamson Ian. 21, 1930 FOREIGN PATENTS 239,988 Germany Oct. 28, 1911

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