US3028104A - Horizontal rotary grinding mill and apparatus inclosing floating-impelling load-rotor - Google Patents

Description

N. L. HALL 3,028,104 HORIZONTAL ROTARY GRINDING MILL AND APPARATUS INCLOSING 2 Shets-Sheet 1 April 3, 1962 FLOATING-IMPELLING LOAD-ROTOR Filed June 26, 1961 O o O INVENTOR. Mix we Apnl 3, 1962 N. HALL 3,028,104

HORIZONTAL ROTARY GRINDING MILL AND APPARATUS INCLOSING FLOATING-IMPELLING LOAD-ROTOR Filed June 26, 1961 2 Sheets-Sheet 2 Fig. 44.

INV EN TOR.

This invention relates to horizontal rotary grinding mill and apparatus of the conical ball mill type used for the comminution, processing, or classification ofrock or granular products. I

The particular application as described in this specification relates to the manufacture and use of a horizontal rotary conical ball mill with a granular load of material to be ground with a grinding media of steel elements used for the comminution of rock or granular products, the material to be crushed or ground being combined with the grinding elements, the combination forming the rotating mill load. The extended application of this type of mill may be used for crushing, grinding, or processing of ore or cement, other uses being for the mixing, classifying, processing and finishing of chemicals, and the agglomerating and pelletizing of granular substances for extension of a processing treatment. The horizontal rotary mill has a wide application in the industries due to its practical shape, low upkeep, efficiency of operation, and high capacity.

Ball mills are so termed in the trade when using balls as a grinding media in the mill load; rod mills when using rods or bars, and tube mills when using balls, or balls and rods in mill of several diameters in length of cylinder.

Conical mills refer to mill of coniform, i.e. cone shaped form of structure. The standard conical mill as the type is known to the trade, has a cylindrical section of uniform diameter terminating in cone sections at the terminals of the cylindrical section and upon which the conical shapes are based.

In the following descriptions the trade name conical and terms will be used. No definite dividing line exists in size reduction between the term crushing and grinding. One is a term of violent'compression, and the other is a compression extended to a microscopic state-the breaking of one part into two, crushing into grinding. The division conforms to the trade parlance, an idiom of common speech.

Ball mills are in common use for fine grinding and may be of the horizontal rotary cylinder of uniform diameter or of the conical mill type and produce a product of over 200 mesh per square inch in screen size. Large steel balls of over 4 inches in diameter are used for crushing in mills approximating 10 feet in diameter, and balls of less than 2 inches in diameter are used for fine grinding.

The collective weight of steel balls will average 300 pounds per cubic foot and with mill pulp, i.e. ore and moisture, filling the voids between the balls, will increase the weight to 400 pounds per cubic foot. Grinding mill will average from to 14 feet or more in diameter with ball mills of two diameter and tube mills of several diameters in tubular length. Mills operate on dry or wet crushing and grinding and tube mills may operate on fine grinding or processing under intense heat.

The common type of power applied for operation of rotary mills is the conventional, i.e. customary type of geared motor drive. For ore reduction, the mine run of ore is reduced in mill of gyratory or jaw crusher types and'pass the broken ore over a coarse screen, termed grizzley or grate, and in turn deliver the undersize'to a primary roll or disc crusher, and then to a primary ball nit ms atent Or- 3,028,104 Patented Apr. 3, 1962 mill of large diameter using large balls, and in turn delivering the product to secondary ball mills using small ball for extreme fine grinding. Rod mills are of the same construction as ball mills and use steel rods or bars of substantially the length of the cylindrical mill interior. Steel rods are of diameters up to 4 inches and a mill load of rods may fill the mill almost to half of the volumetric mill capacity. The long rod are in axial alinement within the mill and turn diametrally of the bar in radial movement with the rod tumbling over the rod load in a position which is out of alinement with the plane of load and mill rotation.

In the following specification the apparatus outlined includes a load-rotor which acts as an impeller, crusher and grinder upon the load in conjunction with the rotating conical mill shell and particularly with the discharge cone section. The rotating rams not only offer a crushing force, but the load-rotor being within itself a rigid construction, and operating within a moving and massive rotating load, can carry the forces over its structure as a unit, for example, one ram of the rotor exerting a downward crushing movement over the load toe with the following ram being enclosed in the upward moving mill load and possessing a force which can be distributed to the preceding ram via the spreader rings to which they are rigidly attached. Mill load are measured in tons and when halted under rotation their interrupted force exerts a concentrated shock upon the transient or movable bodies within the mill.

Horizontal rotary grinding mills have mill cylinders necessarily involved with an inclosed load grinding element; of itself, the rotating mill is a hollow cylinder which does not perform an effective service without the tumbling or revolving action of a contained grinding ele1nentthe combination of a mill cylinder as a unit with a grinding element as balls, rods, rotors or walls as another unit to perform an effective grinding result. The rotating mill cylinder combined with the active grinding elements comprise the mill and apparatus.

Useless each without the other.

One of the objects of this invention is to develop a milling action within a rotating mill which can accommodate a milling load of approximately 50 percent of the volumetrical capacity of the mill cylinder and maintain a sufficient area of the cross section of the mill cylinder to allow for ample working space for milling action.

A further object is to provide a grinding mill which has an open and clear axial area through which the ground fines of the load may pass through and from the mill with a minimum of obstruction.

A further object is to increase the speed of transit of the ground product through the mill thereby reducing the transient time required for the grinding with consequent increase of the mill capacity.

A further object is to provide a mill action which will utilize the maximum cross sectional space of the mill, eliminating quiet areas of non-action, and utilizing the maximum sectional area practicable for milling operation.

A further object is to provide a milling action which develops a classification of milling load to the proper allocation of over to under size to place a properly sized feed in the areas of most efficient action.

Other objects will become apparent as the invention is disclosed.

Referring to the drawings:

FIGURE 1 is a vertical and longitudinal section of a conical mill and apparatus with load in a staticposition partially submerging a rotatable load-rotor BR composed of three spreader rings 7 rigidly supporting three the feed scoop and the discharge funnel.

3 rams 7-a comprising a load-rotor as further illustrated in FIG. 3.

The conical mill cylindrical section is noted by the numeral 1 and the special steel lining plates as 1-0.

The feed cone head is noted as 2 and the discharge cone head as Z-a, with the feed trunnion bearing as 3 and the discharge trunnion hearing as 3a. A frictional hearing is shown although a roll or other type of hearing may be used to suit a bearing of larger diameter at 3-11.

The feed trunnion is fed by the feed scoop 4 with the central inspection opening 4a to provide for a visual inspection of the mill interior between the feed scoop 4 and the discharge opening at 5. I

The mill is operated by the geared drive 6 being driven from the gear pinion and shaft 6a from any suitable motive power as shown in FIG. 2. The mill bearing rotates on the bearing 3 supported from the abutment S with the discharge bearing 3-a being supported by the abutment 8-a.

FIGURE 2 is a cross section of the apparatus under rotation, the view being taken on line 22 of FIG. 1.

The load-rotor of FIG. 2 is shown in operative position with the ram A striking the load toe T, with the ram B in position carrying its proportionate load towards the zenith of the mill interior and delivering the load portion in an over-fall to further strike the load toe T. Between the rams B and C the load is under a forcible movement in rising to the load crest at the line of normal crest NC, theapproxi'mate line of normal cascade.

FIGURE 3 is a cross section taken on line 33 of FIG. 1, showing the load in a static position with the load-rotor partially submerged with two rams B and C all in a starting position.

FIGURE 4 is a part section and elevation of a loadrotor the section being taken on line 44 of FIG. 5, also showing a means of attachment and bracing between the ram and spreader rings.

FIGURE is an end view of a load-rotor with two rams in opposite position, the view being taken on line 5--5 of FIG. 4.

FIGURE 6 is an end view of a load-rotor with three rams attached to the spreader ring, similar to FIG. 5

Referring to the drawings:

FIGURE 1 is a vertical and longitudinal section of a grinding mill of the conical mill type with a half volume load shown in a static position with a load-rotor of triple rams and spreader rings, all partially submerged in the mill load which can be of balls and ore mixture preferably to a half volume capacity. The diameter of the load-rotor outside to outside of the rams is substantially less than the mill interior diameter sufficient to allow at least a 10 percent load cushion to be maintained between the outer edge of the ram and the mill cylindrical lining. The interior diameter of the load-rotor, which is also the centric diameter of the rams and spreader rings is suiticient to provide a free and open zone along the axis of the cylinder for passage of ground product and ore from The feed trunnion 3 has an interrupted thread or vane which advances the feed from the feed scoop to the mill conical section 2 where it is free to enter the mill load under operation, undergo the various crushing and grinding operations, and then pass to the discharge cone for classification of fines to be discharged as the mill product.

The rotating load-rotor rotates in line with the mill diametral rotation and with the mill being on a level plane, and the load-rotor being of uniform diameter, the load action will hold the load-rotor positioned within the length of the mill cylindrical section. The load-rotor rides upon the load with two rams submerged in the load and, under a proper mill loading the load-rotor will be automatically positioned practically concentric to the mill cylinder and will always have a load cushion existing between the ram and the mill shell and lining while the ram is submerged in the load portion. The positioning of the load-rotor concentrically within the mill is substantially automatic. A change of level for the mill apparatus as a whole will alter the action of the discharge conical section in its load classification. This alteration is only slight but it will effect the positioning of the load-rotor within the cylindrical section of the mill if altered to an extreme. No plausible reason exists for a disturbance of load action by a failure to keep the mill substantially level and in balance.

The load-rotor 7 and 7-a floats independently in the load and is not attached to the mill shell but maintains its position with each rotation of the mill and load. The load-rotor is of less diameter than the mill interior, and in general terms, for each four rotations of the mill, the battering-ram will rotate five revolutions in the same period of time, placing the battering-ram with respect to the mill cylinder it is under a constant change, accordingly the wearing action of the ram on the mill lining is never concentrated to the same point but is undergoing a constant variation of positions during mill rotations.

In FIGURE 3 the rams C and B are submerged within the load and virtually combine any movement or slip of load therebetween to hold the load during the mill starting movement.

In FIGURE 2 the ram A is exerting an impact upon the load toe T to consolidate the load existing between the ram and the shell. After ram B carries a load portion to the mill zenith it moves in over-fall towards the load T exerts the same action as previously exerted by the. ram A, and following in sequence ram C will carry' through a like action. 7

As ram C is ascending in FIG. 2, it will serve to carry the load before it and the mill shell and serve to check consequent load-slipping over the mill shell, with portions of the load falling through the open load-rotor and towards the load toe T. Following such actions, the as cending rain will carry a load portion above the normal cascadeslope of 38 degrees from the horizontal and throw the load portion in overfall towards the load toe T.

The various number of peculiar, inherent, and different actions of the mill load are well distributed over the mill section and the load maintains a violent activity in passing through the various grinding phases.

Milling loads vary in weight, size of crush, moisture content, and texture in being hard and soft, and such characteristics will vary over a crushing period of time so that the conditions underlying the crushing of granular bodies will constantly vary, but a close similarity exists regarding the laws governing the falling of such bodies and one set rule for falling bodies in a tumbling load can not be formed for all material being processed, nevertheless there is a practical speed of cascade for a theoretical fall of all bodies and the variation of differences is not extreme.

All ball milling operations should have that slight means for speed adjustment, for the speed of operation is the most important factor to be constantly maintained in all milling operations. The ideal of practical speed is just under 400 feet per minute for the movement of the perimeter of the mill load. Mills will vary in their characteristics and any difference for adjustment required will come between 380 and 410 feet per minute of travel for the load perimeter.

Tumbling mills which operate at a cascade slope of approximately 38 degrees from the horizontal and the common loading of a free cascading ball load is at a 42 percent capacity. The loading of the herein described mill can operate at a loading of 50 percent capacity for the reason of a variety of load actions being involved which serve to open the mill load to action and prevent a sluggish consolidation of load portions in transit. The additional 8 or 10 percent of loading is carried over the mill trunnions and only a portion is carried by the driving gear.

In operation, this invention utilizes the standard conical mill as the operative portion of the grinding mill apparatus in combination with the action of the independently rotating load-rotor, the rotation of the conical mill shell being in alinement with the rotation of the load-rotor with the length of the battering-ram being in alinement with the mill cylinder. The actions of the mill, battering-ram and the mill load are in unison radially. The conical mill serves to motivate the grinding media and the load Within the mill, grinding elements, and the load rotating in uniform radial alinement, with only the processing mill feed and mill product passing in axial alinement to the mill.

Several different milling actions take place within the mill cross section and the various load portions throughout the load receive different milling actions, such as; the impact crushing action as illustrated in FIG. 2 wherein the ram A strikes the load toe T. In practically all milling actions which develop a load toe, there is a change of direction of the part in movement upward to the load crest and then downward to follow the descending mill shell, and during this action the over-fall of the load portion from ram B strikes the load toe and the ram A strikes the load toe with a decided impact which crowds the load toe against the mill shell, consolidating that portion of the load. The rams are held rigidly to the spreader rings and being under motion form an added force to the ram A against the load toe, The ram B has a residual load portion before it which is carried towards the mill interior zenith and then liberated the load portion which passes in over-fall to further strike the load toe T.

As the load portion behind the ascending ram 13 reaches the normal line of cascade slope NC, and being without support from below, the load will fall through and between the spreader rings and towards the line of mill axis. As the load-rotor is advancing with the rams rigidly connected to the spreader rings and serving to form a unit, the advancing ram C will move the load portion before it and the mill shell and lift the load portion with liner plates lining the mill cylinder being devoid of lifters.

The rams are rigidly connected to the spreader rings and serve as a unit carrying the active forces from one portion of the mill sec-tion across to a neighboring ram, and make an active action over the entire load.

The load-rotor is not only a combination of parts serving to crush, grind or pulverize the load but it is an impeller to the load working in combination with the rotating mill and also working in conjunction with the classifying actions of the discharge cone section 2a.

I claim:

1. A horizontal rotary grinding mill and apparatus of the conical mill type, said mill having a clear interior and imperforate shell open at both ends for respective entry and discharge of a transient circulating load of discrete material under processing or comminution, comprising;

a mill cylindrical section of uniform shell diameter interposed between two coniform shell sections, one i at each end of said cylindrical section, said coniform sections basing separately on each end of said cylindrical section and apeXing in open trunnion bearings, said cylindrical and coniform sections with trunnion bearings attached in combination forming a rotative mill unit of single alinement, said mill unit inclosing a centrally open grinding unit of several spreader rings in mill radial position, said spreader rings attached to and rigidly supporting several rams positioned externally to said spreader rings and in mill axial position, said grinding unit comprising an independent and unattached rotative load-rotor of single diameter of less than mill cylindrical interior diameter and of axial length less than said mill cylinder sectional length and greater than said mill internal diameter and in axial alinement to said cylinder and unattached thereto in independent relation, said grinding elements being partly immersed in said mill load containing indiscriminate load grinding media and adapted to rotate radially and independently in random rotative movement within said rotating mill unit for impelling, crushing and grinding action upon said transit circulating load. 2. A horizontal rotary grinding mill and apparatus of the cylindrical ball mill type, said mill having a clear interior and imperforate shell of uniform diameter, open at both ends for respective entry and discharge of a transient circulating load of discrete material to be ground or processed, comprising;

a mill shell of single cylindrical section and of uniform diameter supported for rotation on open trunnion bearings, said mill being adapted to maintain and service a transient circulating load of discrete material combined with a single unattached and independent load-rotor of several rams rigidly attached to several spreader rings, said load-rotor being partially submerged and floating and rotating in an approximate 50 percent volume of indiscriminate load grinding elements disposed within and of said mill and load.

3. A horizontal rotary grinding mill and apparatus of the cylindrical ball mill type, said mill having a clear interior of uniform diameter and imperforate shell, open at both ends for respective entry and discharge of a transient circulating load of discrete material under processing or comminution, comprising;

a mill cylindrical section of uniform shell diameter in single axial alinement rotative upon open trunnion bearings and positioned separately at each end of said cylindrical section, said mill inclosing a single independent and unattached load-rotor of less than said mill cylindrical internal diameter and of length less than the length of said mill cylinder and disposed in axial alinement to float within an inclosed mill load, said load having a combination of mill feed with grinding elements contained within said mill cylinder, said load-rotor provided with several centrally open spreader rings placed in mill radial position with several rams rigidly and regularly attached thereto and projecting outward from the exterior rim of said spreader rings to a diameter of load-rotor less than said mill interior diameter and floating in said mill load containing indiscriminate grinding elements rotating practically concentric to said mill shell and adapted to impel, crush and grind a mill load and provide a protective cushion of load to be regularly deposited between the rams of said load-rotor and said mill shell to serve in unison with the rotation of said mill and load-rotor.

References Cited in the file of this patent UNITED STATES PATENTS 395,140 Hill Dec. 25, 1888

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