US3027104A - Horizontal rotary grinding mill with floating load-partition - Google Patents

Description

N. L. HALL March 27, 1962 HORIZONTAL ROTARY GRINDING MILL WITH FLOATING LOAD-PARTITION 2 Sheets-Sheet 1 Filed Feb. 28, 1961 INVENTOR. %0540 .F

l r w LENE? March 27, 1962 L HALL HORIZONTAL ROTARY GRINDING MILL WITH FLOATING LOAD-PARTITION I oooco oo i u e o o o oo 50 O lo QO OO OOIOO Filed Feb. 28, 1961 United States Patett O 3,e27,104 HORIZONTAL ROTARY GRHNDIN G MILL WHTH FLOATING LOAD-PARTITEON Newton L. Hall, RO. Box 83, Salt Lake City, Utah Filed Feb. 28, 1961, Ser. No. 92,355 4 Clams. (Ci. 241-176) This invention relates to horizontal rotary grinding mill and apparatus used for the comminution, processing or classification of ores, centents, and granular materials.

The particular application as noted in the herein specification applies to the crushing and grinding of ores for the recovery of their mineral content, and for the crushing, and grinding of rocks and clinker for cement production.

The horizontal rotary mill has a wide application in the trades due to its serviceable shape, low upkeep and high Capacity, the applications being also extended for chemical processing, mixing and classification, drying and burning.

The mills are operated With either batch or circulating loads, in a Wet or dry condition, and under a practical speed of 400 feet per minute of travel for the perimeter of the rotating load, using a grinding medium, the mill load being intermixed with a load of long steel rods, substantially the length of the mill cylinder, or, rods of less than diametral length, and with or without steel balls ranging from one to five inches in diameter. The mill load is composed of crushed raw ore with mill pulp plus the grinding media. The mill load to be crushed or ground varies from a mine run of ore having been crushed in breakers of the jaw or gyratory type, with the ore being passed over a grating or grizzley removing the undersze which is later reduced in a roll or disc crusher, the product being passed to a primary ball or rod mill for reduction to a screen size of six mesh which is'then passed to a secondary ball mill for fine grinding to less than 200 mesh for screen size, a reduction which makes possible a liberation of the fine mineral content of the ore, or a fine size reduction required for a cement rnixture.

This application outlines a Construction wherein the impelling feature to the ball mill load is formed by providing an unattached and independent fioating loadpartition, a dividing wall as a load partition, extending longitudinally within the cylindrical section of the mill shell serving as a rotor to impel a general division of the mill interier With its load to virtually form two semicylindrical load sections.

The compartment wall division can be formed of various means, as a ,collective combination of short length rods extending radially in consecutive alinement in line with the mill axis, (as described in my co-pending applicationfiled in the United States Patent Ofiice on December 16, 1960, Serial No. 76,195) or, as in the herein application as a closed face load-partition, and/ or as au open face load-partition with the various forms of divided actions within the load being substantially similar.

The` closed face load-partition has a mid-portion of thin thickness or width to oil'set excessive weight and to provide an anchorage to the central portion embedded in the load to hold the load-partition concentrically to the mill cylinder and to provide an anchorage to prevent the load-partion from striking the mill shell lining, and also to effect a cushioning to the action as the exposed lateral ram of the load-partition strikes the load toe T. The reduction of load-partition weight is a feature of economy in cost of special steels for the wear on the hard facings and special steels is an expensive item in mill operation. A load-partition of open face not only oiters an additional economy in weight and in cost of steel but it also provides a passageway in aXial alinement for the mill product in its transit through the mill.

One of the objects of this invention is to provide a crushing and grinding mill that is rugged and serviceable, is simple of Construction and contains within itself the essential parts for operation without the incorporation of extraneous parts to effect milling results of high Capacity, and to produce those results efliciently and economically.

Another object is to provide a mill wherein the circulating load can obtain efilcient processing and pass through the rnill in unobstructed transit.

Another object is to provide a mill structure with parts which can be detached and altered to a practical eXtent from the exterior of the mill.

Another object is to provide a mill wherein the weight of the mill structure, its linings and load are uniformly distributed and balanced in line With the mill length, not only balanced, but having a weight that is contained within itself and does not requre a duplicate part to balance or equalize its ofiset or specific weight.

A further object is to provide an open loadpartition wherein the grinding impact rams can be of wear resisting steel with the connecting bars forrned of common steel.

A further object is to develop a crushing efiect which is absorbed in screen range to a grinding effect, that is, crushing to grindng, without a distinction of screen size therebetween.

A further object is to provide a grinding mill With a,

r'loating load-partition wherein the load-partition attains indiscriminate positions in axial algnment with the mill shell under successive rotations.

Other objects will become apparent as the invention isdisclosed. 1,

In the drawings: I j FIGURE 1 represents a vertical longitudinal 'section of a conical mill With'load and a closed face load-partiton, the sectionbeing taken on line 1-1 of FIG. 2 with the load-partition being inmersd in the load partially and all in a static position. r

FIGURE 2 is a cross section of a conical mill with a closed face load-partition, the section being taken on line' 2-2 of FIG. 1, the load being shown in a static position.

FGURE 3 is a cross section taken on line 3-3 of a FIG. 1, showing the closed face load-partition in an advanced position over FIG. 2 with the load being under partial action, the main gear, pinon and Operating shaft for motive power being shown partially.

FIGURE 4 is a side elevation of an open face loadpartition fol-med of two lateral impact rams with connecting rods in between.

FGURE 5 is a cross section of an open face loadtaken on line 5-5 of FIG. 4 showing a design partition of construction to be made by fornng the impact rams of wear resisting steel attached to spreader arms of common steel, the intervening space between the opposite rams aording an open passage to the grouud product in passing in an axial direction to the mill discharge.

FIGURE 6 is a vertical longitudinal section, similar to FiG. 1, showing a conical grinding mill with open face ioad-partition in vertical and axial position and alinement, the mill cylinder being shown without lifters.

FIGURE 7 is across section taken on line 7 7 of FIG. 6 showing the open face load-partition in a vertical position with the mill load in Outline under normal mill rotation.

FEGURE 8 is a cross section taken on line 8-8 of FIG. iS showing the open face load-partton in a horzon- 4 tal radial position with the exposed impact ram in posi- 3 tion to strike the load toe T and with the mill load shown in Outline, the ram being in an advanced position to the load shown in FIG. 7. The mill driving gear and pirion being shown partially.

The connecting features of the structural mill parts such as bolts, rivets, welds or other means are not shown, the various ccnnections being made according to well known structural practice.

In the drawings:

FIGURE l is a vertical longitudinal section of the conical mill with unattached closed face load-partition shown partially immcrsed in a static load, wherein the conical mill shell is noted by the numeral 1, and the steel mill lining as l-a, the feed end coniform head being noted as l-b and the discharge end coniform head as l-c. The mill shell is supported by the feed open trunnion hearing 2, and the discharge open trunnion bearing 2-a. The feed scoop is noted as 3, with the central detachable head as 3-a. The driving gear is noted as 4, the driving pinion as 5 mounted on the pinion shaft S-, FIG. 3 The mill is operated by any suitable motive power.

The floating and unattached closed face load-partition is noted as 6 with its reduced section or middle portion as 6-a, the enlarged rim portion being noted as 6-b. The load shown in a static position is noted as 7, FIGS. l and 2 with the oversize feed portion as 7-a and the undersize discharge portion as 7-b.

The classification of the load is noted in the cylindrical mill section of nniforrn diameter as 7-a'. The open discharge hood is noted as 8. The mill structure rests on the abutments 10 at the feed trunnion and IO-a at the discharge trunnion.

In FIGURE 3 the arrow 9 represents the radial throw produced by the edge terminal of the load-partition in its partial position advancing to strike the load toe T in forcible impact.

FIGURE 4 is a side elevation of an open face loadpartition with the similar and opposite impact rams being noted as 12 and the spreader bars as 13, with the removable attaching pin as 13-a.

FIGURE 5 is a cross section of an open face loadpartition taken on line 5-5 of FIG. 4 showing the design for a method of attachment for the impact ram 12 to the spreader bar 13.

FIGURE 6 is a vertical longitudnal section of a conical mill, similar to FIG. 1 wherein the conical mill shell is noted by the numeral 1 and the mill lining plates as l-a, the open face load-partition being noted as 12-13-13-a. The mill load with its diferent classifications is noted as 7-a, 7-a', and 7-b. The arrow R' notes the central open space between the cylindrical and conical sections of the mill providing a maximum zone for contact between the different mill actions allowing a freedom of passage of the undersize for classification and discharge through the open trunnion and from the mill. The discharge grate 8-a is attached from the exterior of the mill and upon its removal provides a mill entrance for installation or repair and with its large opening avoids the necessity for a manhole entry. Rotary mills present a blind operation and the ease for inspection and entry for repair ofiers a distinct advantage.

FIGURE 7 is a cross section of a mill taken on line 7--7 of FIG. 6, showing the open face load-partiton in a vertical axial position with the mill load shown under a normal flow.

FIGURE 8 is a cross section of a mill taken on line 8--8 of FIG. 6 showing the mill load under an active rotation with the mill crest breaking to a sliding cascade and with the open face load-partition advanced to a horizontal position to strike the load toe T in forceful impact, the opposite ram of the open face load-partition being submerged and held within the load to prevent a radial movement and a meeting of the exposed opposite ram With a striking of the mill lining or shell at the horizontal' position. The load-partition is never free from the load with either impact ram being enclosed and sub' merged in the rising portion of the load.

A main driving gear is shown in part as 4 with the driving pinion as 5 mounted on the power shaft S-a to offer an Operating speed of rotation governed by the nor mal speed of rotation approximately 400 feet per minute of travel measured on the perimeter of the rotating load,- the general average of speed of mill rotation varying according to the mill shell load diameter. A mill of Seven feet in diameter and rotating approximately 20 revolutions per minute will produce a proper cascade to the mill load action. The mill lining plates will wear and cause a larger mill diameter producing an enlarged circumference to the load and requiring an adjustment of mill speed to maintain the practical speed of rotation.

The horizontal rotary grinding mill cylinder with its several parts, plus the grinding elements such as ball or rod, floating load-partition, and, under certain milling practices, the oversize ore, can form the milling apparatus.

Similar reference characters refer to similar parts in all of the views.

In operation:

The conical type of grinding mill possesses the merit of affording a classification of the load during the erushing action.

The rotating cones have a natural action of classification equal to a screening action and the cylindrical section with its uniform diameter, has a natural action to concentrate the oversize towards the perimeter of the load, features which are provided by the shape and form of the mill cylinders and acting without the use of any extraneous features such as a screen or grate within the mill cylinder.

The mill lining plates l-a, FIG. 2 are shown with lifters l-' and without lifters in FIGS. 1 and 3. Mills being started for rotation possess a sluggish inertia and the loads of certain compositions require extra lifters to grip the load and place it in full rotation. Other loads have a density and weight that overcomes a slipping of the load over the mill lining.

A large variety of grinding media may be used but the common steel ball from one to five inches in diameter will meet most requirements. In a conical mill the undersize of ball and load tends to follow the interier surface of the mill shell and towards the apex of the cone. The oversize tends to move towards the load zone of greater diameter and to the cylindrical mill section.

It is essential that the floating load-partiton type of mill be maintained, during operation, with the loads on each side of the wall practically equal and well balanced.

When loads are unequal on either side of the wall, and during rotation, the action of the loads will be to remain in unbalance resulting in the formation of a large ball load on one side and a smaller ball load on the other side of the wall, the effect being to pass the mill feed to the side having the smallest ball load Where it will receive the least grinding action. When the mill is under rotation an unbalanced load will remain in unbalance from the fact that loads of different size have different actions during rotation and the short time of a single rotation does not permit the loads to interchange and become balanced. Placing an equalizing slot extending from wall to wall of the mill and placed midway along the wall length will provide an opening for a portion of the load to freely pass from one compartment to the other and maintain the load in balance. (Re: United States Letters Patent, filed Aug. 22, 1950; Ser. No. 180,752; N. L. Hall, Pat. No. 2,653,769-September 29', 1953). The open face load-partition has a mici-portion of wall open, and excepting for the spreader bars, entirely free for passage of the axial portion of the mill load.

The open face of the load-partition maintains the load as a unit and acts to balance the mill load at all times of rotation.

The cylindrical section of the mill with its several impact actions provides the general tendency of the mill action to create a general distribution of the load with the oversize towards the enclosing mill shell and the undersize towards and alongside of the compartment wall.

As the load-partition rotates, each striking edge of the partition and each impact ram repeats the impact action following in dual order and the forces acting to throw the striking edge, or the impact ram, of the partition against the mill lining and shell are held in restraint by the opposing edge of ram which is held by being embedded in the rising portion of the load so as to hold the partition substantially concentric to the mill shell, the reverse of actions retaining the wall in its central position upon the completion of each single load rotation. When the striking rim or impact ram is in position to strike the load toe T, in the direction of the arrow 9 to load toe T, it is practically at the maximum position for radial action and throw extending from the mill zenith.

A common circulating ball mill action virtually demands a mill loading sized to less than 50 percent of the volumetric Capacity of the mill, a frequent loading being at 42 percent Capacity, such a loading being frequently limited by the open discharge of the mill trunnion. It is essential that a mill load have suflicient working space for cascading or over-fall action in the mill space above the load and the extreme of loading for a circulating load rarely meets a loading of 50 percent Capacity. A further condition being, that an enlarged mill load with its pulp will work against the entering feed at the feed trunnion.

The crushing or milling action of the freely floating and unattached load-partition is a striking of the load toe with a concentrated weight, actng twice for each revolution of the mill, and is an action resembling a stamp action within the mill plus any grinding action of attrition from' balls which may be contained within the load, whereas, the action of impact or attrition of the ball load in plain cascade is decidedly different and is one with an insignificant impact action, all of which is practically within the load cascade. The two actions are dissimilar, for they act upon the load being treated in manners giving different results for extractions.

Milling actions of crushing and grinding have been given, by the trade, a Classified term of impact and attrition, but such divisions of classication are frequently unjustified.

An impact blow upon a piece will divide one piece into two and in so doing will also produce extreme fines from the fractured area of the piece, without any action of attrition.

Similar divisions following will produce fines during the piece reduction, the several impacts being devoid of attritive and a rubbing of peces upon each other. The fines of fracture are always present and never absent upon impact actions.

The action of the floating load-partition produces results upon the load which may be considered as both of impact and attrition.

The loading of the mill load using the oating and unattached load-partition preferably should be maintained within 50 and 55 percent of the mill capacity to secure the best results of cone classification and grading and to secure a mill action of high Capacity, due to the fact principally that the actions in descent of the impact rams are independent of the size of the mill load, the advantage of the floating load-partition type can be from 8 to 10 percent above the Capacity of the plain ball mill.

I claim:

l. A horizontal rotary grinding mill of the conical mill type of clear inten'or and imperforate shell open at both ends for respective entry and discharge of a transient circulating mill load of discrete material, comprising;

a conical mill shell of cylindrical mid-section and opposi-te coniform end sections based on said cylindrical mid-section enclosing a normal mill load of grinding elements plus mill feed and pulp, said load partly immersing a single unattached and independent open face load-partition, said load-partition. being partly submerged in said load and held to diverse positions by said mill load under consecutive mill rotations, said positions being substantially concentric and in axial alinement to said mill shell cylindrical section, said load-partition having a width less than the clear internal diametral width of said mill interior and a longitudinal length less than the length of said cylindrical mill section, said mill being adapted to contain and employ a transient circulating load of material to be processed or ground.

2. A horizontal rotary grinding mill of the conical mill type of clear interior and mperforate shell open at both ends for respective entry and discharge of a transient circulating load of material, comprising;

a conical mill shell of uniform diametral mid-section intermediate to opposite coniform end sections, said mill containing a normal mill load of material in transit, and grinding elements including a single independent floating open face load-partition Unattached to said mill interior, said milling apparatus being adapted to comminute, classify, segregate and discharge said transit load within and from said conical mill under normal speed of rotation and load saturation.

3. A horizontal rotary grinding mill of clear interior uniform diameter, and imperforate shell open at both ends for respective entry and discharge of a circulating load of discrete material, to be ground, comprising;

a cylindrical mill shell encl-osing a normal mill load with grinding elements plus mill feed and pulp, said load partly immersing a single unattached and independcnt closed face load-partition, said load-partition being partly submerged and held to diverse positions by said mill load under consecutive mill rotations, said positions being substantially concentric and in aXial alinement to said cylindrical mill shell said load-partition having a width greater than one half of and less than the clear internal diametral width of said mill interior and a longitudinal length less than the length of said cylindrical shell, said mill being adapted to contain and employ a composite circulating load of material to be processed or ground.

4. In a horizontal rotary grinding mill of clear interior uniform diameter, and imperforate shell open at both ends for respective entry and discharge of a circulating load of discrete material, comprising; r

a mill shell of uniform diameter with mill load of grinding elements plus mill feed and pulp, said grinding elements comprising a grinding ball load plus an unattached `and independent oating and rotatable load-partition, said load-partition being' partly im mersed in the rising portion of said mill load, said floating and rotatable load-partition being held to positions substantially equal in diametral spaces from either rim or impact ram of said load-partition and said mill shell lining, said mill being adapted to comminute a circulating load of discrete material.

References Cited in the file of this patent UNITED STATES PATENTS

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