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May 3, 1938. F. E. MARCY 2,115,820 BALL MILL Filed July 27, 1936 4 Sheets-Sheet 1 3mm 6. 9% May 3, 1938. F. E. MARCY 2,115,820 BALL MILL Filed July 27, ‘1936 ‘4 SIhQets-Sheet 2 May 3, 1938. F_ E’ MARCY 2,115,820 BALL MILL Filed July 27, 1936 4 Sheets-Shget 3 Patented May 3, 1938 2,115,820 ' UNITED .STATES PATIENT" OFFICE " Application '~ Frank 1:.Ill]! ‘ ?st-fame», 27, ausszo 1936, Serial No. _ 92,887 ' 3 Claims. This invention relates to ball mills and is par . ticularly directed to improvements in means for discharging‘ materials from ball mills. A principal object or the invention is the pro 5 vision of means for the discharge of materials from ball mills whereby the content of mate rial in the mill may be maintained substantially constant at a predetermined amount regardless . of ?uctuations or surges in the feed to the mill 10 or in other operating conditions. A further object of the invention is to provide ball mills having discharge means of simple and rugged construction which are e?‘ective and de pendable in their operation. Another object -of the invention is the pro vision of means for the discharge of materials from ball mills whereby the height of the dis 15 charge may be varied to a substantial degree without ailecting the level of the material in the 20 ball mill. 7 . - i Other objects and advantages of the invention will be apparent from the detailed description of illustrative embodiments of the invention herein after appearing. . 25 The, invention is particularly valuable in con nection with ball mills operated with a relatively‘ small mill content or with a low “pulp line”, which has been found by a number of yearsoi.’ experiment and practical operation to be the 30 condition under which ball mills operate at the greatest capacity and efdciency. of Fig. 13; and - ~ I Fig. 15 is a fragmentary partial section on line i5—l5 of Fig. 14. . ' . 1 In Figs. 1 and 2, I6 is the shell of a ball mill provided at the discharge end with a drilled ?ange ii, and hawng an annular boss l2 on which is mounted a tire I 3 whereby the mill is supported for rotation upon rollers it. The mill is driven by conventional means, not ‘shown, which may be located at the feed end of the mill. “Inside the shell are provided liner membersv i5, 15 and adjacent the end of the shell there is pro vided the discharge grate assembly it. ‘The discharge grate assembly includes a plu rality of grate sectors i7, shown in further detail in Figs. 3-5, connected by means “described here inafter into a strong, rugged annular grate, readi 20 ly removable for repairs and replacements. The grate sectors ll, comprise a plurality of rolled steel bars l8, positioned in parallel align ment and in suitable spaced relation by means of side plates I 9 to which the bars are welded. The positioning of the hers is aided and the structure is strengthened by spacing pads 28 suitably placed between and welded to adjacent plates. . The sector is further strengthened by means of rods 20 which may be welded to both scribed for thepurpose of illustration with ref erence to the accompanying drawings in which: Fig. 1 is a fragmentary elevation in partial taching thesectors to the shell of the mill and for connecting them together into the grate as Fig. 3 is a front elevation and Fig. 4 is a side elevation of a discharge grate section of the form shown in Figs. 1 and 2; Fig. 5 is a fragmentary view in partial section showing a detail of the discharge grate section 45 of Figs. 3 and 4; '_ Fig. 6 is an elevation of a bottom closure mem-' ber; Fig. '7 is a perspective view of an angle brace of the'embodiment of Figs. 1 and 2; Fig. 8 is a fragmentary elevation of the dis 50 charge end of a ball mill provided with a modi ?ed form of discharge grate; '. Fig. 9 is a fragmentary sectional view of the form of the invention shown in Fig. 8, taken on Cl CA the line 9—9 of Fig. 8; Fig. 10 is an elevation and Fig. 11 is a side view of a three-scoop discharge device which may be used in connection with the ball mills of Figs. 1 and 10; j > on the discharge side thereof and serve for at semblies. \ . The sectors are advantageously connected to. Fig. 2 is an end elevation of the embodiment shown in Fig. 1 with the end plate removed; 60 , m Fig. 14 is a fragmentary section on line [4 ‘the bars and the side plates. As is indicated, the side plates l9 "project beyond the‘grate bars bodying the principles of the invention; - tion of another form of discharge grate embody ing the principles of the invention; The invention will'be more particularly de section of the discharge end of a ball mill em 40 (cast-‘9) m Fig. 12 is an end view and Fig. 13 is an eleva the shell by means of angle braces 2| (see Fig. '1) , the bolts 22 attaching the braces to the sectors also serving to connect adjacent sectors together 40 at ‘their peripheral ends. The central ends of the sectors are similarly connected by bolts 23 passing through side‘ plates IQ of adjacent sectors and advantageously the same bolts pass through lugs 25 of an annular center plate 28. ~ 45 The space between the peripheral ends of the sectors and the shell Ill oi‘ the mill is closed by clamp bars 26 (see Fig. 6) thrust ‘against the peripheral end bars of the grate sectors by means of screw bolts 2?. ' 50 A particularly valuable feature oi’ the grate of the invention is'the progressive variation in the openings between the bars which has been found to be very advantageous in-maintaining a sub stantially constant pulp level in the ball-mill; 55 By increasing the width of the openings in the grates towards the center of the grate the rate of discharge increases very rapidly as the pulp level rises and clogging of ‘the mill with surges in the feed or other variations in operating con 60 2 2,115,820 ditions is eliminated. This is particularly valu able in dealing with thick pulps since with such materials the rate of flow increases more rapidly with increasing area of the discharge opening than is the case with ?uids like water. For example, in a grate having fourteen bars, the ?rst 7 openings nearest the peripheral end a may advantageously be % inch, the next 11; inch, and increasing progressively to H inch at the central end. In general, the openings between the grate bars may be varied from openings of, for example, 1/8 to % inch at the peripheral end to openings of, for example, 1/2 to 1/4 inch at the central end of the sectors. Where the speci?cation and claims refer to the progressive variation in the width of the slots in the grate, this shall include structures in which each slot varies in width from an ad jacent slot as well as those in which the progres 20 sion is in stages with several slots in each stage of the same width. ' , The material ?owing through the grate may advantageously be discharged, for example, to a launder not shown, through an annular opening 25 at ‘the periphery‘ of the discharge end of the shell formed between the annular spout member 29 and end plate 30 ‘spaced from the spout mem ber- by means of spacers 3| or bolts 32 which fasten both the spout member and the end plate to ?ange Ii of shell "I. - The door 33, centrally located in end plate 30, provides an advantageous means for inspecting the discharge grate during operation of the ball mill. The door can be removed or replaced dur ing operation by pressing button 34 in handle 35, which retracts catches 36 through levers 31. The catches when extended engage the inside of the circular opening in door 310 or any suitable cir cular holder mounted thereon. 40 If it is desired to discharge the eiliuent from. the ball mill at a point above the bottom of the mill the spout member 29 and end plate 30 may be replaced by a scoop discharge device such as is shown in Figures 10 and 11. This device is 45 shown by way of example with three scoops ll, which lift e?luent material from the peripheral wall 42 and discharge it through the central sating annular bulge or convexity 55, the thick ness of which is proportioned to the normal amount of wear on the grate ends at various points along the radius. The center of the grate is preferably left open to provide a manhole which may be closed by a manhole cover 56 bolted to the grate. A further form of grate sector is shown in Figs. 12 to 15. In this form of sector the bars 6| are welded in spaced parallel relation to side plates 10 62 which are positioned at an angle of approxi mately 66° to the longitudinal faces of the bars. Spacing pads 63 are provided as in the grate sec tor shown in Figs. 3-5, and rods 64 welded to the bars and side plates further strengthen the sec tors. The bars are preferably spaced at distances increasing from the periphery towards the center ,as described in connection with Figs. 3-5. The sectors may be connected into a grate as sembly by means of a spider and suitable con— 20 necting elements as shown in my U. S. Patent No. 1,629,803. I claim: 1. Discharge means for ball mills adapted to automatically regulate the rate of discharge so 25 as to maintain a substantially constant low level of material in the mill regardless of variation in the rate of feed comprising a grate member mounted adjacent the discharge end of the drum of the ball mill, said grate having a plurality of 30 discharge openings in the form of elongated slots positioned with their longitudinal axes along chords of said drum, the width of the slots pro gressively increasing from the periphery of the drum towards the center and the slots adjacent 35 the center being substantially wider than those adjacent the periphery whereby to substantially accelerate the discharge of material through the grate as the level of material rises in the drum above the desired low level. 2. A grate for ball mills adapted to automati cally regulate the rate of discharge in relation to the height of material in the mill, said grate com prising a plurality of sector shaped units, each of said units comprising a pair of side members, a 45 plurality of grate bar elements supported in spaced relation between said side members to de spout 43. The outer wall of the discharge device line a plurality of elongated slots, the spacing is advantageously provided with hand-holes 44. between said bars progressively increasing in 60 By the use of this device the ei'?uent material may width towards the inner end of the sector and be discharged at within 5 or 6 inches below the the space between the bars adjacent said inner end being substantially greater than between the center of the mill. ~ Figs. 8 and 9 show a one-piece grate 56 which bars adjacent the outer end whereby the rate of may replace the grate assembly l6 shown in Figs. discharge of material from the mill will be sub stantially increased with the‘ rise of the level of 55 1 and 2, and which includes a number of valu material within the mill. able improvements. The grate consists of a sin 3. In a grate for ball mills adapted to auto gle annular member, having an external diameter slightly less than the internal diameter of the matically compensate for variations in the rate shell ill of the ball mill. It is provided with a of feed by automatically regulating the rate of 60 plurality of slots 5| cut or cast therein‘. The slots - discharge in relation to the height of material in are arranged in a plurality of segmental groups. the mill, a grate sector comprising a pair of side They extend along chords of the annular grate members, a plurality of grate bar elements se and may be designated as chordal slots. The cured at their ends to said side members in spaced parallel relation, spacing pads secured be slots 5! preferably vary in width from the periph 65 ery towards the center, as described in connec tion with Figs. 3-5. The grate may be attached to the shell of the mill by means of bolts 52 passing through holes in lugs 53 spaced about the periphery of the 70 grate. The grate is tightly positioned by means of wedges 54 which are preferably bifurcated to fit around bolts 52. These wedges greatly facili tate the installation and removal of the grates. An advantageous feature of the grate shown in 75 Figs. 8 and 9 is the provision of a wear-compen tween adiacent bars, said pads progressively in-K creasing in thickness from the outer to the inner end of the sector and the space between said bars being correspondingly increased so that the space between the bars adjacent the inner end of the sector is substantially greater than be 70 tween those adjacent the outer end thereof whereby the rate of discharge of material from the mill is substantially increased as the material in the mill rises above a desired level. II'RANK E. MARCY.