US3030036A - Ball mills - Google Patents

Description

April 17, 1962 Original Filed Sept. 29, 1955 E. CHAPMAN BALL MILLS 7 Sheets-Sheet 1 INVENTOR. Everelf (3%62/9772627? PARKER & CARTER ATTO RNEYS April 17, 1962 Original Filed Sept. 29, 1955 E. CHAPMAN BALL MILLS 7 Sheets-Sheet 2 IN V EN TOR.

liz/erezz" Cider avian PARKER 2,. CARTER ATTO RNEYS April 17, 1962 E. CHAPMAN 3,030,036

BALL MILLS Original Filed Sept. 29, 1955 '7 Sheets-Sheet 5 A INVENTOR. 56 Everet {J/ PARKER & CARTER A ORNEYS April 17, 1962 E. CHAPMAN 3,030,036

BALL MILLS Original Filed Sept. 29, 1955 7 Sheets-Sheet 4 l I o go 102 I? i 86 6. o

IN VEN TOR.

PARKER 5 CARTER ATTORNEYS E. CHAPMAN BALL MILLS April 17, 1962 I122v J I f 1 I40 I36 I 7 Sheets-Sheet 5 IN V EN TOR.

Ever? h C'kapman PA R KER 8. CARTER AT TO R NEYS April 17, 1962 E. CHAPMAN 3,030,036

BALL MILLS Original Filed Sept. 29, 1955 '7' Sheets-Sheet 6 I64 66 I64 I 156 I F & [1g 3 w I INVENTOR. 154 Z 170??? ('kapmaze PARKE R 2 CARTER ATTORNEYS April 17, 19-62 E. CHAPMAN 3,030,036

BALL MILLS Original Filed Sept. 29, 1955 7 Sheets-Sheet '7 INVENTOR. Zvereiz C72 apmaie PARKER 2, CARTER ATTORNEYS United States Patent 3,630,636 BALL MRLLS :Everett Eliaplnan, West Chester, Pa., assignor to Nordberg Manuiacturing llompany, Milwaukee, Win, a corporation otWisconsin Continuation of application Ser. No. 537,376, Eept. 29, 1955. This application Dec. 23, 1959, Ser. No. 86L42 "ZhQlaims. (Ell. "241-475) :bowl, chamber or'track is rotated in one direction about 'oneaxis butin the opposite direction about a second axis.

.The speeds of rotation are such that material undergoing grinding and a chargeof grinding elements in the chamber are ranged aroundthe inner surface of the chamber by artificial gravity due to centrifugal force and at the same time the charge and grinding elements are sloshed or .oscillated at a preselected trequencyto create a violent grinding action within the enclosed mass of material and elements.

With the general disclosure of that application as a background, one Ofdhb primary objects of my invention is animprovedform of what I shall term a generally up- :right gyratory grinding device in whichthe grinding chamber is rotated about one axis by a power means separate from a second power means which rotates th chamber about a second axis but constructed so that the first power means operates at constant speed.

Another object is a grinding chamber and'table structure generally ofthe above type in which the chamber or grinding bowl has a depending hollow shaft which serves both as a support and as a discharge for ground material.

Another object is a new and improvedstructure for controlling the operation of such a grinding bowl.

Anotherobject is a grinding bowl of the above type with its associated structure in which the bowl will be stationary, relative to the base, when only the table is be ing rotated.

Another object is a grinding device of the above type with means for quickly and easily varying the grinding angle between the two axes.

Another object is a grinding device of the above type characterized by a new and improved form of discharge for ground material.

Another object isa grinding deviceof the above type in which artificial gravity, due to centrifugal force, is set up in the bowl by a constant speed power source and slosh or oscillation of the material undergoin grinding is eltected by a separate variable speed power source.

Other objects will appear frorrrtime tortime in the ensuing specification and drawings in which:

FIGURE .1 is a side View of one'forzn of .my device;

FEGUREQ. is an enlarged viewsimilar to FIGURE 1, but'with .the details ofthe base and bowl omitted and showing the'driving connections, in section;

FIGURES is a partialsection of the bowl usedwith my'device;

FIGURE 4 is asection of 'an' alternate bowlform;

FIGURE 5 is an intermediate supporting platform or stool, in:section, with a number ofalternatives;

2 FIGURE 6 is adiagramrnatic showing of a control circuit and drive for the device in FIGURES land '2;

FIGURE 7 is-a section similar to FIGUREZ of a modi- FIGURE '8 is another variant shown in section; and

FIGURE 9' is still another-variant.

In-all of the forms illustrated, thebowl is indicated 'by the letter B, the base by the letter F, andthe table by the letter T.

'In FIGURES 1 and -2, the table T has'a platform 10 supported by a suitable bearing 12 on-the base through adepending hollow shaft Moithelike. The table is 'powered by a suitable-electric motor -16, or otherwise, which is geared ina suitablemanner to a shaft'ld for "driving thetable-shaft-de through suitable gearing Ztl.

A'gear housing'ZZ in the base encloses the above gear- -ing with'a portion 24 of the table shaft extending through the housing by a'suitable bearing 26. This bearing is held in position by a threaded nut 23, or the like, with a seal 30, and the-exposed end of thetable shaft carries a plu rality of slip rings 32 suitably bolted or otherwise held in position.

A stool or platform M yshown in detail in FIGURE 2, ismounted in alongitudinal-groove in the upper surface of the table and is composed of-a suitable frame-like structure withtop plates 36 disposed at an angle to each other and defining a mounting socket.

The grinding chamber orbowl'B is mounted on a plate 38 which is-screwed or otherwise secured to a hollow shaft 40 forminga tubular outlet and support for the bowl. Asgear box 42 surrounds the shaft with'upper and lower bearings e i and 46 so that the bowl can rotate freely. A suitable electric motor 48 or the like is mounted on andextends at a suitable angle or is disposed in'any suitable position on the gearbox and is adapted to drive the bowl through suitable gears 50. A suitable lock ring. Ell is threaded to the lower end'of the hollow shaft to seal and hold the lower bearing 46. A replaceable wear resistant sleeve 52 is held in the inside of the-hollow shaft by a flange 53 which is locked in a groove between the bowl and shaft, and a suitable guard orscrew element 5 E may extend above it intothe chamber to allow passage of ground material butto block the grinding balls. The platform'or stool 34 has suitable openings in its sides at 55 and inthe bottom at 56, so that appropriate leads .canbe carriedup from the slip rings 32 to the motor 48.

It should be noted'by this structure thatthe table T is driven by apower source which is mounted on the base or frame, while the bowl power source takes the form of anelectric motor mounted on thetable. In this form, the bowl motor can be used as an effective counter-weight has the additional advantage that a novel control can be eitectedIto'be explained in detail hereinbelow.

it should benotedin'FIGURE 1 that the table rotates about. a generallyuprighta-Xis X concentric with its shaft 1 Thebowlrotatesabout a second axis Y inclined to the first axis X, concentric with-the hollow outlet sleeve 4t), .andintersecting the first axis atthepoint Z generally at the geometricceuter of the grinding chamber orbowl.

11 have referred to the chamber or grinding track as a :bowhand inusing that term in theclaims, it shouldbe understood that I do not intend for the term'necessarily to cover only a perfect sphere. Thisis particularly true since I have found thatan asymmetric 'bowl other'than a perfect sphere is very-desirable-under certain circumstances,-depending-upon the-size'of the unit'involvecLthe type of-material undergoing grinding, therotative speeds desired, whether grinding wet or dry, and the grinding angle used.

The bowl-might bemade up of a. number of sections or halves. For example, 'I might use three tops "and three bottoms, each set including a long top and bottom, a regular or spherical top and bottom, and a short top and bottom. Each lower half has an axial opening which is adapted to line up with the hollow outlet shaft 40, while each upper half has an axial opening which forms an inlet. The upper half 58 and lower half 59, bolted together at 69, or welded or otherwise secured, may be considered to represent a perfect or near perfect sphere in FIGURE 3. I might elongate or shorten either half or both axially along the vertical axis while retaining the same equatorial diameter. Thus, the slosh action of the balls and material undergoing grinding encounters a changing radius of curvature above and below the equator if either a long or short top or bottom is used. I might use a top and bottom which are both short. Or I might have them both long. In either case, the cross section would be an ellipsoid. On the other hand, I might use a long top with a short bottom, or a short top with a long bottom. Or I might combine either with a regular or hemispherical top and bottom. Thus, by combining all possible tops with all possible bottoms, I provide at least nine possible bowl shapes, any combination being usable with the unit shown in FIGURES l and 2. One of the important points behind these bowl shapes is that they are constructed to be easily and equally interchanged on the gear box so that if the grinding conditions change, a new chamber may be substituted to meet the changed grinding conditions.

In FIGURE 4, I have shown a part of a bowl half in which the bowl is formed in three sections 69, 70 and i1, welded or otherwise connected at 72, and the middle sec ion may be a hardened steel wear belt because the grinding is done in this zone. Also the bowl halves in FIGURE 3 could be of different material and/ or hardness if most of the grinding was done in one half.

The bowl angle-the angle between the axes X and Y-is also an important factor, and I have found it desirable to construct my unit so that this angle can be easily changed. In FIGURE 5, I have shown one form of platform or stool which slides into the longitudinal slot in the table 10. The upper surface of the platform is divided into two plates 73 and 74 which come together at 75. The plates converge and define an angle between them which serves as a saddle or support for the gear box 42 on the how], a corresponding angle being formed on the lower surface of the gear box. The gear box and stool or platform may be connected together by suitable screws or bolts along the outer edges of the engaged plates or by any suitable means. The platforms might be varied, however, by rotating both of them, in unison, about the center point 75. Thus, the bowl angle between the axes X and Y will be changed. For example, if the forward plate 73 is raised, the rear plate 74 would be lowered, or vice versa. But the angle between them would remain the same to smoothly mesh with the bottom of the gear box 42. When the gear box is mounted on a different platform or stool, the axis Y of the bowl will intersect the table axis X at a different point, and the platform or stool can be shifted in one direction or the other to again bring the intersection of the axes to the point Z in the general geometric center of the bowl. The specific structure of the stool or intermediate platform in FIGURE 4 is, of itself, unimportant, except that the use of a plurality of such intermediate stools, each giving a different bowl angle, provides a quick adjustment for the bowl angle and, during operation, a rigid mounting for the bowl, regardless of the angle in use. Depending upon the masses of the elements involved, the table and the edges of the stool or platform could be appropriately graduated so that the operator would merely have to position any selected stool in a previously marked position which would automatically bring the intersecting point Z to the geometric center of the bowl.

As is fully explained in application Serial No. 511,665,

the method of grinding involves rotating the table in one direction and the bowl in the other, each about their respective axes. In my construction, if they are rotated at the same speed but in opposite directions, the bowl surface will have no differential rotation relative to the base or ground, and no grinding will take place. To operate such a unit, the bowl must be rotated at a speed substantially in excess of the table speed, so that the difference between the two speeds will be sufficient to centrifugally range the material undergoing grinding and the grinding elements preferably balls, about the inner surface of the bowl. The centrifugal force desired is dependent on the diameter of the bowl and from this the effective bowl speed can be determined. The effective bowl speed is the difference between the actual bowl speed and the table speed, and therefore the speed imparted to the bowl by its motor must be equal to the desired effective speed plus the table speed. In short, the differential speed or effective bowl speed equals what I term the artificial gravity set up on the contents of the bowl due to centrifugal force.

I find it highly desirable in grinding to maintain this artificial gravity constant, regardless of the table speed, and in FIGURE 6, I disclose one form of apparatus or control mechanism which can be used as a single lever control which will simultaneously increase or decrease both the bowl speed and table speed while maintaining a constant speed differential. The table, indicated diagrammatically at T, is driven through suitable gearing by its motor 16. The bowl motor is indicated at 48, and I have not shown the details of the bowl or gear box for clarity. Both the bowl and the table motors are provided with 3 phase, A.C. tachometer generators 84 and 86 which are suitably connected to 3 phase motors 88 and 90 by leads 92 and 94. A differential 96 with the usual driver and driven bevel gears 98 and 1% and pinion gears 102 is disposed between the 3 phase bowl and table motors. The bowl 3 phase motor drives the driver gear 98, while the table 3 phase motor Q0 is geared to the pinion cage 164 Thus the output shaft 106 from the driven gear refleets the difference between the input speeds of the bowl and table 3 phase motors.

To translate this speed differential into control energy for the bowl motor 48 so it will automatically respond to changes in the table speed, a suitable speed governor 198, possibly of the old and well-known flyball type, may be driven by the shaft 106 through suitable gearing so that the output from the fiyball frame adjusts a suitable spring 116 which variably compresses a carbon pile 112. The carbon pile is connected in series in a circuit which includes a suitable source of power 114 and a generator field winding 116 for a generator which supplies current through suitable contacts A-B connected to the armature of the bowl motor at CD in any suitable manner, not shown. The variable compression of the spring is thus translated into a variable resistance in the carbon pile, in effect a rheostat, so that the voltage supplied by the generator 116 is varied to the bowl motor.

Thus a speed differential can be pre-set, and if the speed of the table motor is increased, which normally would decrease the speed differential, the flyball governor immediately increases the voltage supplied to the bowl motor by the generator 116. Thus the speed differential will remain the same even though both the table and bowl speeds change.

In FIGURE 7, I have shown a variant form of drive in which the bowl motor is mounted on the base, not on the table, either next to or otherwise suitably arranged with respect to the table motor. In any event, a drive shaft 118 extends from the table motor and is suitably geared at 120 to a hollow table shaft or stub 122. A second drive shaft 124 from the bowl motor extends through the hollow stub and is supported at its upper and lower ends by suitable bearings 126 and 128, the lower bearincorporate dust seals.

=motors are :mounted on I the base. .tages ofthe FIGURE1-6 formis that the angle between ring having aretaining nut 130. A similar retaining-nut .132 connects a suitable lower bearing 134 for the'table .stub whichis alsoprovided with an upper bearing 136. .A gear housing 138, .possibly similar in many respects .ldliand 144 .onthe table and may be provided with a seal at 145. This shaft carries a'bevel gear 146 which is .driven by a bevel gearI-td on the input shaft 124 through .and .idler lfitlmounted in any suitable manner on the .table.

One of the important advantages 'of this-arrangement is that therspeedof the table does not have to be sub- .tracted from the bowlspeed before the bowl will rotate relative to the base. .The gears 145 and 143 are of thesame size,.have thesame pitch and the same number :of.teeth,*and;are what l term equal. Whenthe bowl mo- .tor is not .energizedand the table motor is rotating the :table, .the bowl will float around .thedriving gear 143 :and will maintain its-samerelative position, due to the idler 15d and the fact that the gears 146 and 148 .are the same size. .Any input to'the driving shaft from the bowl motor will immediately be reflected in positive rotation .of.the'bowl. In short, the bowl does not have to initially overcome the speed of the table before it can produce augmented gravity forces onthe. balls.

.InFIGURE 8, Ihave showna further'modification, similar to "FIGURE 7, in that both the table and bowl One ofthe disadvan- 'the axes of the bowl and table must besplit or divided by theidler.axisandthe.angleisfixed in the bevel gears. To .overcomethisQI mountasecond shaft .152 in the gear housingorbox which is connected to the bowl motor in- ,putshaft 154by a constant speed variable angle universal joint-156. lt-should .be noted that this joint ishoused in thelhollow tableshaftllSSand the driveis carried to .thebowl by equal gears I60 and 162 through an idler 164. .By using a constantspeed universal joint, thebowl angle can be changed ..by use of a different stool. Other than this, the details of the gear box, .frame andbowl :can be the same .or slightly modified to accommodate the universal joint and its associated driving structure. For example, asupport or platform .164 may be used in the. gear box to support the idler and one end of the shaft 152 through-a suitable bearing 166, the other end of the shaft being supported at 168 to the top of the gear box. In this form, I again emphasize that due to the idler gear the speed of the table motor does not have to be first overcome by the bowl motor, and all speed put into the bowl by its-driving means will be immediately effective to augment gravity regardless of the table speed. effect, the bowl speed which produces augmented gravity on theballsis totally.independentofthe table speed.

In FIGURE 9, I have shown a further modification, similarrin many ways to FIGURE 8 in that the universal joint and second shaft are used, but in this form the idler isreplaced by a chain drive at 170 which also makes all offthebowlmotor speed immediately effective to set up the artificial gravity, regardless of the table speed. When using a chain drive ofthis nature, the sprockets should have equal diameters, and the same number of teeth. Thedrive tothe bowl shaft could also be a compound idler between spur andbevel gears or any other gearing or drive that produces the above efliect.

While I have shown and described the preferred form and several modifications, it should be understood that numerous changes can be made without departing from the inventions fundamental theme. Several of the modifications are interchangeable. For example, the bowl forms or shapes in FIGURES 3 and 4 can be used with any of the drives. The specific constant speed differential in the chamber dueto. rotation of thetable.

imechanismin FIGURE 6 representsonly one form. In

the claims I have used the term bowl and it should "be understood that I intend this term'to define a generally spherical bowl or possibly axially elongated or shortened or an asymmetric combination of shapes, such as suggested in FIGURE 3. The word bowl does-not necessarily mean a perfect sphere. The term bowl angle refers to the angle between the bowl axis and the table axis.

The term artificial gravity refers to the centrifugal force imparted to the material undergoing grinding and the grinding elements in the chamberpar- 'tialiy due to the bowl motor.

I are as follows:

This invention is a specific improvement and an addition to the method and apparatus shown inSerial No. 511,665, and it is my intention to augment that inventive disclosure by one or more inventive features .or steps.

.I have shown a separate drive for the grinding bowl which can be mounted on the table, and .undercertain circumstances this is very desirable. .that the drive of the bowl, such as shown in FIGURES It should be noted 7, 8 and 9, essentially is an epicyclic gear or drive train.

It is also an object of my invention to provide a variety of bowl shapes composed of a combination of bowl zones or halves, welded, bolted and/ or composite metallurgy,

.each combination being specifically intended for a par- .ticular grinding situation. Thisis further augmented by .a mechanism for quickly and :easily varying the 'bowl angle. I also providea number of motordrives whereby .the rotative speed from-the .bowl motorisentirely effective to set up artificial gravity in the bowl, regardless of the speed of the table. I also provide an improved form ofdischarge for the b0W1,'WhICh substantially eliminates any discharge problems and at the same time serves I as a support for the bowl.

It should be noted that .by..my structure, the bowl motor canbe a constant speed A.C. unit for any particular grinding assembly, as the artificial gravity created .in the bowl should be constant, for example, from 6 to'9 gravities. The slosh impartedto the material undergoing grinding can be determined by varying the speed of the table motor which, by experiment,-is one of the. most important variables when encountering different ores. The slosh speed defines the typeof ball motion, which canthus be selected over a wide range of different actions. By the various arrangements shown, the bowl motorcan operateat aconstant speed, so that regardless of the sloshimpartedto'the material, the artificial gravity applied to the material will be constant.

I claim:

1..In a .device for grinding, a base, a'table rotatably mounted on the base about a generally upright axis, a

/ grinding bowl rotatably mounted on thetable, power means for'rotatingthe table, and a'second power means on the table for rotating the bowl independently of the rotation of'the' table.

2. The structure of claim 1 in which the grinding-bowl is mounted on the table about a'second axis'incliued to the table axis and intersecting it generally at the geometric center of'the'bowl.

'5. In a grinding mill,"abase,' atable'rotatably mounted on the base about a generally upright axis, a grinding chamber rotatably mounted in the table about an axis inclined to the first, power means for driving the table and chamber, the chamber being open at its upper end to receive material to be ground, and a hollow outlet shaft extending from the lower end of the chamber into the table concentric with the inclined axis.

4. The structure of claim 3 in which the hollow outlet a shaft is mounted in the table and functions as the support for the chamber.

5. In a grinding device, a base, a table mounted for rotation on the base about a first axis, a bowl rotatably mounted on the table about a second axis, power means for rotating the table in one direction, a second power means for rotating the bowl in the other direction, and means for automatically maintaining a predetermined speed difference between the table and bowl speeds as the table speed varies.

6. The structure of claim in which the bowl axis intersects the table axis generally at the center of mass of the bowl.

7. The structure of claim 5 in which the second power means for the bowl is mounted on the table.

8. In a grinding device, a base, a table mounted for rotation on the base about a first axis, a bowl mounted for rotation on the table about a second axis, power means for rotating the table in one direction and the bowl in the other direction, and means for automatically maintaining a predetermined speed difference between the table and bowl speeds as the table speed varies.

9. In a ball mill, a base, a table mounted on the base for rotation about a predetermined first axis, a grinding chamber mounted for rotation on the table about an axis inclined to the first axis, power means for rotating the table, a second power means for rotating the chamber, and a driving connection between the second power means and the chamber including a constant speed joint.

10. The structure of claim 9 characterized by and in cluding a second shaft in the table which is disposed generally parallel to the inclined bowl axis, the joint being connected to the second shaft, and a driving connection between the second shaft and the bowl.

11. The structure of claim 10 in which the driving connection between the second shaft and the bowl includes a chain drive.

12. The structure of claim 10 in which the driving connection between the second shaft and the bowl includes a gear drive.

13. The structure of claim 12 in which the gear drive includes equal spur gears for the bowl and second shaft, and an idler between them.

14. In a grinding mechanism, a base, a table mounted for rotation on the base about a generally upright axis, a bowl mounted for rotation on the table about an axis inclined to the table axis, power means and a driving connection between it and the table, a second power means and a driving connection between it and the bowl, and means for maintaining the bowl stationary relative to the base when only the table power means is in operation.

15. The structure of claim 14 in which said last-mentioned means includes a chain drive in the driving connection between the second power means and the bowl.

16. The structure of claim 14 in which a driving shaft extends from the second power means, and including equal gears for the driving shaft and bowl with an idler between them.

17. The structure of claim 16 in which the gears and idler are spur gears.

18. The structure of claim 16 in which the gears and idler are bevel gears.

19. The structure of claim 16 in which the driving shaft includes a constant speed joint.

20. In a ball mill grinding device, a base, a table mounted for rotation on the base about a generally upright axis including a removable platform, a grinding bowl mounted for rotation on the table about a second but convergent axis defining a predetermined angle with the first axis, the platform having mounting surfaces to support the bowl at the predetermined angle, driving connections for rotating the table and bowl, and power means for the driving connections.

21. The structure of claim 20 in which the bowl power means is mounted on the table.

22. In a device for grinding material, a base, a table mounted for rotation on the base about a predetermined axis, a grinding bowl mounted for rotation on the table about a second axis convergent with the first, variable speed power means for rotating the table, and constant speed power means for rotating the bowl.

23. The structure of claim 22 characterized by and including means for holding the bowl stationary relative to the base when only the table power means is in operation.

24. In a ball mill, a base, a sub-base mounted for rotation on said base about a predetermined axis, a mill body mounted on said sub-base for rotation about an axis inclined to and convergent with the axis of rotation of the sub-base on the base, said mill body having a ball track circumferentially described about and generally concentric with the intersection of the two axes, and a discharge from said mill body including a generally rectilinear tube concentric with the axis of rotation of the mill body.

25. The structure of claim 24 characterized in that the tube passes through the sub-base and discharges at a level beneath the sub-base.

26. The structure of claim 24, characterized by and including bearing means for the mill body, surrounding the discharge tube.

27. In a ball mill, a base, a sub-base mounted for rotation on said base about a predetermined axis, a mill body mounted on said sub-base for rotation about an axis inclined to and convergent with the axis of rotation of the sub-base on the base, said mill body having a ball track circumferentially described about and generally concentric with the intersection of the two axes, motor means for rotating the sub-base in relation to the base, and separate motor means on the sub-base for rotating the mill body in relation to the sub-base.

28. In a grinding mechanism, a base, a table mounted for rotation on the base about a generally upright axis, a bowl mounted for rotation on the table about an axis inclined to the table axis, power means and a driving connection between it and the table, a second power means for the bowl, and a driving connection between the second power means and the bowl including an epicyclic drive train.

References Cited in the file of this patent UNITED STATES PATENTS 706,102 Pendleton Aug. 5, 1902 721,649 Pendleton Feb. 24, 1903 1,295,726 Garrow Feb. 25, 1919 1,519,475 Altorfer Dec. 16, 1924 1,780,915 Hardinge Nov. 11, 1930 2,500,908 Symons Mar. 24, 1950 2,798,675 Limb July 9, 1957 FOREIGN PATENTS 490,845 France Ian. 14, 1919

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