US2516161A - Vertical axis ball mill with flexible wall and impact means to receive material fromthe flexed wall - Google Patents

Description

July 25, 1950 H. H. 'r kaovs 2,515,151

VERTICAL AXIS BALL HILL WI FLEXIBLE WALL AND IIPACT MEANS TO RECEIVE HATERIAL FROM THE FLEXED WALL Filed Nov. 7, 1945 5 Sheets-Sheet 1 July 25, 1950 H. H. TALBOYS 2,516,161v

VERTICAL AXIS BALL MILL WITH FLEXIBLE WALL AND IIIPACT MEANS TO RECEIVE MATERIAL FROII 'n-lE FLEXED WALL Filed Nov. 7, 1945 5 Sheets-Sheet 2 sq 1720?)? to?" N fiiery zfirZays July 25', 1950 H. H. TALBOYS 5, 6

VERTICAL AXIS BALL HILL WITH FLEXIBLE WALL AND IMPACT MEANS TO RECEIVE MATERIAL FROM THE FLEXED WALL Filed Nov. 7, 1945 5 Sheets-Sheet 3 Jiarn eys.

July 25, 1950 H. H. TALBOYS 5 VERTICAL AXIS BALL IIILL wrm, FLEXIBLE IALL AND nlPAc'r ms '10- RECEIVE MATERIAL FROI 'mE FLEXED IIALL Filod 80v. 7, 1945 5 Sheets-Sheet 4 jnz/enzor jyekry/f 7kloya 5 M M .lZ/orneys.

July 25, 1950 H. H. TALBOYS 6 VERTICAL AXIS BALL IIILL IITH FLEXIBLE WALL AND IMPACT IEANS TO RECEIVE FROII THE FLEXED IALL Filed Nov. '7, 1945 5 Shoots-Sheet 5 In 0'67? for wiffarwys.

Patented July 25, 1950 OFFICE.

VERTICAL AXIS BALL MILL WITH FLEXIBLE WALL AND IMPACT MEANS TO RECEIVE MATERIAL FROM THE FLEXED WALL Henry H'. Taiboys, Milwaukee,

Wis., assignor to N ordberg Manufacturing Company, Milwaukee, Wis., a corporation of Wisconsin Application November '1, 1945, Serial No. 327,255 18 Claims. (Cl. 241-49) My invention relates to an improvement in ball mills or fine grinders, and has for one purpose to provide a ball mill of improved efiiciency.

Another purpose is to provide a ball mill having an enlarged output per unit of power employed.

.Another purpose is to provide a ball mill with associated screening means.

Another purpose is to provide an improved ball runway or track in which an important part of the grinding takes place.

Another purpose is to provide a ball mill having a yielding track or wall.

Another purpose is to provide a ball mill in which the distortion or bending of a yielding rotated wallis employed to direct the charge against a relatively fixed impacting element.

Another purpose is to provide improved impacting means for use in connection with a rotated ball mill.

Another purpose is to provide improved feed means for a ball mill.

Another purpose is to provide improved means for withdrawing the finished product.

Other purposes will appear from time to time in the course of the specification and claims.

The invention is illustrated mOreor less diagrammatically in the accompanying drawings wherein:

Figure 1 is a, side elevation with parts broken away and parts in vertical section;

Figure 2 is a partial vertical section on an enlarged scale;

Figure 3 is a section on an enlarged scale on the line 3-3 of Figure 2;

Figure 4 is a section on an enlarged scale on the line 44 of Figure 2;

Figure 5 is a section on an enlarged scale on the line 5-5 of Figure 2;

Figure 6 is a partial vertical section on an enlarged scale;

Figure 7 is a partial vertical section through a variant form; and

Figure 8 is a partial horizontal section through a variant form.

Like parts are indicated by like symbols throughout the specification and drawings.

Referring to the drawings I generally indicatesthe surface or floor upon which the device is mounted. 2, 2, indicate supports resting on the surface I. 3 generally indicates a transversely extending base member which may be an I-beam. 4 indicates a pair of upwardly extending channels located at each end of the base formed by the member 3. 5 indicates a top frame member. 6, 6 are transversely extending supports of any suitable number or shape, resting on the bottom member 3. Resting upon the annular support 6 is a bottom plate 1 of a lower or product receiving housing having a circumferential outer wall 3, a circumferential inner wall 9 and a top wall ill, with any suitable internal braces II and l2. l5? l5 indicate removable access plates or gates for the housing A. It will be noted that the inner wall 9 is located below the inner edge of the top wall I0 and is provided with yielding sealing rings l'l aligned with corresponding'sealing rings is at the inner edge of the upper wall Ill. The purpose of these sealing rings will later appear. Mounted on the transversely extending supports 3 is any suitable hub or split sleeve l9 adapted to receive the fixed central post 20 which terminates upwardly at 2|. Keyed to the upper reduced end of the member 20 is the sleeve portion 22 which has an upper portion 23 of increased diameter which may be square in cross section and is provided with a plurality of discharge outlets 24, as shown for example in Figures 2 and 5. 25 is a hollow sleeve, 'aligned with the post 20 and including a lower portion 26 extending within the squared portion 23 of the sleeve 22, and held against rotation in relation thereto. It may be held at its upper end, for example in any suitable split sleeve or gripping and supporting member '21. Its hollow interior is aligned with any suitable funnel 28 through which material to be ground may be delivered. As is clear in Figure 2 the material delivered through the funnel 28 passes downwardly through the hollow of the sleeve 26 and out through the feed apertures 24, incidentally filling the hollow portion of the sleeve 22 to the level of the apertures 24. Surrounding the sleeve 25 are roller or ball bearings 30, 3| about which rotates the outer sleeve 32. Surrounding the lower fixed post 20 are additional ball or roller bearings 33, 34 about which rotates the lower outer sleeve 35, to which may be secured any suitable gear 36 in mesh with the pinion 31 on the drive shaft 38, with its pulley 39 about which pass any suitable belts 40 driven by the drive pulley 4| from any suitable motor 42. The shaft 38 may be rotatably mounted in any suitable bearings 43, 44 on any suitable frame members or supports 45 and 46. The sleeve 35 has an upper fiange 41, to the lower face of which the gear 36 is secured by bolts 48 which pass through the bottom fan plate 49, the outer edge of which is engaged in sealing'relation by the flexible sealing rings above described. 50 indicates curved fan blades shown for example in Figure 4, which overlie the outer edge of the fan plate 48, the top of the blade spaces being enclosed by the upper slightly conic plate M which abuts, in sealing relation, against the above described sealingring I8. The fan linet is provided with an internal ring 52 and an outer ring 53 which may be mounted unitarily with the top plate The spacebetween the upper edges of the members 52, 58 may be covered by any screen ring 54 the purpose of which will later appear. The screen 54 may be omitted and certainly should not be used if its presence under any circumstances interferes with the separating action of the sharp edged separating ring 55. Mounted at the upper edge of the outer ring 53 is an abutment or separating ring 55. Spaced upwardly from and supported by the plate 49 by supporting spacers 56 is an upper plate 51. 'As a matter of convenience, and to permit adjustment, the supports 58 may be screw threaded into the plate 49. Bolts 58 with nuts 59 are employed to hold the plate 51 in position at the top of the spacers 58. The plate is shown as having an upwardly and outwardly inclined edge portion 60 and a. downwardly projecting centering ring 6| extending within the upper edge of the inner fan access ring 52, and maintaining a closure throughout a predetermined range of vertical adjustment. The upwardly inclined portion 60 is provided with a plurality of. generally radially extending vanes 62. 63 is a screen spaced above the plate 51. This screen constitutes a bypass means for bypassing oversized material, for regrinding by the below described wall or belt 86 and the impact structure which includes the below described impact plate I24. It may be mounted at its inner edge in a ring 64. At its outer edge it is mounted on or secured to an upwardbr and outwardly inclined solid ring portion 65 having vertically extending vanes 66 and terminating in a horizontal feed delivering portion 61. The screen 63 may be supported by generally radially extending arms 68 which extend from the ring 64 to the ring 65. At the ends of the arms 88 may be vertical supporting legs 18 located for example at the inner and outer ends of the arms. These may be secured in any suitable manner to the plate 51, whereby the entire above described fan and screen structure rotates as a unit. It will be observed that there is a slight clearance between the inner edge of the plate 51 and the opposed outer face of the sleeve 22, the sleeve 22 being held against rotation.

The above described annular structure constitutes'a directing or conveyor or discharge ring which serves to convey and direct the centrifugally moving particles toward the inner surface of the below described member 86. The ring overlies the outer edge of the plate 51, which constitutes a delivery plate for the material upon its surface. Only coarser particles which pass over the edge of the delivery plate can cross the gap about the exterior of said plate.

Mounted on the upper rotating sleeve 32 is an outwardly extending top disc held for example by screws 16 against rotation in relation to the sleeve 32. Extending downwardly from the disc 15 are supporting screws 11 which are in screw threaded engagement with lugs 18 outwardly extending from a ring 19 from which extend radially and downwardly the arms 88, to the outer ends of which is secured thering 8|. The ring has an upper annulus 82, which may be of fabric or any suitable sealing means and which extends within the upper cylindrical housing wall 83 which in turn is secured to the top wall or closure 84. It will be observed that a vertical adjustment of the ring 8| is thus permitted, without breaking the seal formed by the ring 82. The ring 8| has an outwardly extending flange 88 which receives 5 one edge of the flexible housing member 86. The opposite edge of the member 86 is received by the outwardly extending flange 88 of the ring 81 which surrounds the above described ring 53 and is held by any suitable securing means such as the lock ring 88 illustrated in Figure 6. The housing or grinding wall or outer member 88 is shown as being concave and generally arcuate in generally radial section. It is formed of flexible material and may for example be made of a tire carcass with cord impregnated with rubber, or flexible material such as rubber without cord or fabric inserts. In the use of the device it will be observed that as material is fed downwardly through the funnel 28 and outwardly through the apertures 24 it is delivered to the space surrounded by the flexible grinding wall 88. It moves centrifugally outwardly across the screen 68 and is delivered across the discharge member 61. When the device is being rotated within the proper range of speed, the material to be ground with any suitable supply of balls 88 is centrifugally held in the space surrounded by the concave surface of the side wall or grinding wall 86, as indicated in Figure 3. The under size material may pass downwardly through the screen 88 and outwardly over the discharge member 51 and 68 to pass downwardly into the fan space defined by the rings 53 and 52. As during rotation the fan vanes 50 are efiective to direct a substantial blast of air, the fine particles will be carried through the fan structure and into the circumferential disposal chamber A. The coarse particles pass out to the grinding space and are ground, as will later appear.

A primary part of the grindingaction is cotained by causing the centrifugally held mass of particles undergoing grinding, with the associated balls 90 to move inwardly from the wall 86 and violently strike a fixed impacting assembly. Centrii'ugal force holds the material against the wall 66, which accelerates it and gives it the proper speed of movement, for a free excursion which ends in an impact. In the particular embodiment of the invention herein shown I employ an inward distortion of the wall 86 to project the accelerated charge of balls and particles against any suitable impacting means. In order to cause an inward fiexure of the side wall 86, I illustrate the following structure. 95 indicates a roller 5 adapted to engage and inwardly distort the wall 86, as shown for example in Figure 3. The roller 95, with its spacers 88 is mounted between the upper fork member 91 and the lower fork member 98, as by any suitable centering rod or shaft 5 99. Any suitable bearing means may be employed, not herein shown in detail. The upper plates 98 and 98 are connected by a vertically extending plate use which in turn is secured to the plate 18! pivoted for rotation about a center de- 35 fined by the vertical shaft 102. The bearing assembly may be mounted on any suitable base plate I83 which in turn is secured to the vertical support 8. The roller 95 may be adjusted toward or away from the axis of rotation of the wall 86, 70 for example by the link i0 3 pivoted at one end on the member I 85 on the roller supporting structure, and passing at its other and through a sleeve 506 which in turn is mounted on a pivot I01, clamped by the member I88 to the opposite 7 side 0! the vertical support 4. The handle I88 1 controls a screw threaded nut II 0, which is effective to increase or diminish the effective length of the radius rod I04. thus moving the roller 05 toward or-away from the center of rotation of the sidewall 85. Normally the roller 35 engages the wall 83 but it may be outwardly withdrawn for purpose of adjustment or removal.

Whereas-in Figures 2 and 3. I illustrate a single roller 95, it will be understood that it may be desirable to employ additional rollers. For example in Figure '7, in connection with a single flexible element 86a, I illustrate two rollers 95a and 05b one roller engaging an upper portion of the member 8611 and the other roller engaging a lower portion. Whereas the axes of the rollers 05a and 35b are inclined to the vertical it will be understood that the arrangement or alignment of axes may be widely varied, and both axes may be generally vertical. In the form of Figure 8, I illustrate an even larger number of rollers, namely the two upper rollers 35c and two lower rollers 35d opposed to the flexible member 86b. It will thus be understood that I may substantially vary.

the size and proportions of the flexible member 86, 80a and 86b and may oppose to it one or more rollers, with the rollers, when two or more are employed, being located, if desired, at different levels, and with different axes. The inclination of the axes in Figures '7 and 8 is somewhat exa gerated, as it is in general advantageous to have the axes not too much inclined to the vertical, in order to permit a proper alignment of the receiving or impacting member. In Figures 7 and 8 I have not illustrated the receiving assemblies but it will be understood that they may be substantially'identical with that shown in Figures 2 and 3 with anysuitable changes orlvariations in proportion and location necessary to receive the charge from a plurality of rollers.

Locked to the exterior of the squared portion 23 is a supporting plate I20 for the below discribed impact structure. At its outer edge is a generally vertical pivot I2I which carries a plate I22 to which is secured the impacting member generally indicated as I23. The impacting member has a rear wall I24 and an outer or side wall I25, herein shown as unitary therewith and somewhat inclined with relation thereto. As will be clear from Figure 3 the walls I24 and I25 may sleeve I illustrate for example the duct I40 which may extend upwardly through'the hollow of the sleeves 25 and 25 to any suitable control valve I which controls the delivery of fluid under pressure along the duct I42 to anysuitable source not herein shown. The details of the hydraulic or pneumatic contro1 do not of themselves form part of the present invention, it being understood that any suitable control, hydraulic or pneumatic, or mechanically, may be employed for varying the angular relation between the two above described impacting members. I43 is any suitable release. 7

It will be clear that when the roller 05 is in the position in which it is shown in Figure 3, it will cause the accelerated charge of balls and particles to move inwardly along a path which causes it vide, in effect, a species of horizontally extending trough having an open inner end I23. It will be understood that the plate I20 is upwardly spaced above the line of delivery of impacted material inwardly through the open end I28. I29 is a second impacting member," mounted on the supporting plate I20, as for example by the flange I30.

It has a side wall I3I and an end wall I32 and may also have a top wall I33 and bottom wall I34. In order to control the impact assembly, I may employ any suitable means such as the'hydraulic cylinder I35 with its outwardly extending piston connection I35 carrying a link I31 pivoted to any suitable pin I38 mounted on the supporting plate I22 of the first impacting member. I may employ the cylinder. I35 to control the position and angle of the impact member I23. It should be positioned to receive the free stream of material delivered by the inwardy bulge of the flexible wall 85, caused by the roller, 95, all direct ploughing action being avoided. The member I23 is also inwardly withdrawn when the mill is starting or shutting down. Any suitable means to strike against the impact member I24, after a free flight, with a violent impact. The imp'acted materialv will then follow generally the path indicated by the arrows in Figure 3 and will impact the side wall I3I of the second impact member I29. It will then be deflected and will impact the end wall I32 of said second impact member and may even be delivered outwardly at sufficient speed toimpact against the charge moving with the flexible wall toward the zone of deflection caused by the roller 95. Such. material as drops to the screen surface 63, will, if of sufllciently small size, pass through and be delivered outwardly due to centrifugal force, by

the solid plate 51. The finer particles which passv over the outer edge portion 30 will be drawn by suction through the gap between 52 and 53, and will be delivered downwardly and outwardly through the fan vanes 50. I may use a screen 54 in the gap between 52 and 53, but it can be omitted, if desired. The fines will be delivered into the circumferential passage or box A and may be removed therefrom by any suitable means not herein shown. It will be understood that I may omit the vanes 50 and may use any other suitable means for maintaining the air flow.

It will be understood that, whereas, I have described. and'illustrated' a practical and operative device, nevertheless many changes may be made in the size, shape, number and disposition of parts without departing from the spirit of my invention. 1 therefore wish my description and drawings to be taken as in a broad sense illustrative or diagrammatic, rather than as limiting me to my precise showing. For example, the

use of impact members or balls with many materials may be omitted.

However, in the structure shown, I illustrate a composite grinding and classifying or separating device having a grinding component, which includes the flexible member 86 and the parts surrounded thereby, and a fan component including the members 50 of Figure 4.

The use and operation of the invention are as follows:

In starting the device the impact member I23 may be moved to an inwardly withdrawn position where it is out of line of the movement of the charge with the wall 36. A suitable charge of balls or other members is provided. These balls cannot escape downwardly from the chamher since their escape is prevented by the screen elements 54. As the rotor is brought to speed the balls will ride in the hollow of the inner face of the flexiblewall 86. Feed is delivered downwardly through the sleeve 26 and outwardly through the discharge apertures 24. The matefor controlling the cylinder I35 may be employed. as rial to be fed will be centrifugally urged out- Wardly by rotation of the plate 51 and the screen 63. When the rotor'is brought up to speed, and feed is flowing, the roller 95 and the impact member III are positioned for example as shown in Figure 2. The charge will tend centrifugalLv to hug the surface of the flexible wall or belt 85. However, the inward bulge or deflection of the wall 85 which is caused by the roller 95 will project the charge, in a free flight which diverges inwardly from the surface of the wall or belt 86. The roller 95 is moved sufiiciently inwardly against the wall 88 to obtain the desired inward deflection of the new highly accelerated mixture .of balls and material against the impact structure which includes the plate I24. The speed of rotation may for example be of the order of 160 R. P. M. or up to 200 R. P. M., depending on the'diameter of the member 86, and on the desired peripheral speed. The material travels at high speed across the inward bulge of the wall 85, the inward travel of the mixed charge of particles undergoing crushing and of balls 80, being in the nature of a free flight. The impact member I24 is so set as to be inthe line of delivery of the material and terminates the free flight of the material with an impact. The impact against the member I24 may be a glancing impact, or it may be a full face" impact. Thereafter, the balls'and particles will take the general path indicated by the arrows in Figure 3 and wiil reeeive a secondimpact by contact with the wall l3l of the impact member 129. The parts may be so set as to cause a third impact against the wall I32. The halls and the larger particles, or possibly the balls alone, may continue their free flight until they impact against the mass of material which is moving about with the wall 86 toward the bulge created by the wheel 95, creating another impact. If there are any particles of sufilcient mass to travel with the balls they also will impact against the mass and will be reimpacted against the member I14. The fines will tend to fiow downwardly through the screen 53 to the solid disc 51. These finer particles, unless of sufllcient coarseness to jump the gap over the screen 5! by centrifugal acceleration, will be drawn downwardly through the fan vanes 50 and will reach the chamber A for removal. The coarser particles which do not pass through the gap between 52 and 53, will be centrifugally delivered again to the wall 86.

The sharp inner edge of the ring 55 is effective to provide a sharp and accurate division by size of the fine particles. The oversize, which passes above the sharp edge of the ring, goes out to the member 85, for further reduction; The fine particles, which pass below the edge, escape through the gap. In this connection in some circumstances it may be advantageous to omit the screen 54, to prevent any impairing of the separating action of the sharp inner edge of the ring 55. The vanes 52 are efiective to throw all particles across the gap at substantially the same speed. Each particle crossing the gap is acted upon the air flowing at relatively high velocity downwardly through the gap. Also, the settling rate of fine particles in air varies with the size of the particles. Hence the larger particles are not deflected enough by the downwardly rushing air to be carried below the separating sharp edge of the ring 55. I can obtain a remarkably accurate classification. by varying the width of the gap, or by varying the height of the inclined ring 60 in relation to the knife edge ring I! or by usins both. factors of adjustment.

1 bypass means for oversize particles, may under some circumstances be omitted, or may be variously proportioned, or made radially adjustable,

to suit the desire of the user. In Figure 6 the outer edge of the member 61 overhangs or is vertically aligned with the inner edge of the member 53. .The outer edge of '57 may be vertically aligned with 53, or may be even farther out from-the center, to prevent a splash of flying oversize particles from discharging through the gap with the fines. It will be ,understood that this relationship may be varied. For example the member 61 may either be omitted altogether or may be substantially shortened, radially, to provide a gap through which the finer particles may readily be downwardly drawn into the fan area.

However, it is not in general advantageous to permit any of the material that passes outwardly on the screen 63 and over the ring 65, 51, to be drawn downwardly through the gap and discharged. Preferably only material which has previously passed downwardly through the screen 63 is permitted to flow outwardly through the gap, for the above described process of classification. It will be understood that the screen 53 may be much coarser than the fines to be discharged. Some coarser particles must accompany the fines, to keep the fines from sluggishly staying on the plate 51. On the other hand, if too much coarse material goes through the screen 63 and onto the plate 51, there may be such a mass of material moving across the gap that an undue proportion of the fines will be carried over. Also too much material will not only shut off the air passage, but will create a movement of air across the gap and at least partially neutralize the effective velocity and volume of the classifying current of downward moving air. The gap may be somewhat varied, to suit the particular problem involved, the air velocities employed, and the speed of rotation used.

The width of the ring 55 can be varied. to control the width of the gap or the discharge lip of the ring 60 may be radially extended. Generally this need not be a matter of adjustment, but of initial setting or design. Once a width of gap is determined for a certain grinding job, the width may be kept constant, as a mill is usually designed for continuous service on one product and on one size of product. However, it will be understood that either the member 60 or the member 55 or both, may be varied in size in order to control or change the width of the classifying gap between them, if a change of the material treated is made. The parts may be so designed that the heavier particles, the particles which call for further grinding, will jump the gap over the edge 55 and will be reground. The particles which have reached the desired fineness will be unable to jump the gap 55 and will not be able centrifugally to resist the tendency of the air to draw them down into the fan vanes 50.

The structure herein shown includes several cooperating elements and features. In the first place, the wall- 85, the means for feeding the material to be ground and the means for rotating the rotor constitute a ball mill in which a charge of balls and material to be ground is centrifugally conveyed upon the inner face of the well 8.8. and undersoes some grind ng. Then the balls and the material undergoing crushing are moved inwardly from the face of the conveying wall 86 for an impact against the relatively fixed impact member, this constituting an impacting component or step, with a sequence of separate impacts. A further impacting step results from the return of balls and material to the concave wall or track.

A positive classification by size action takes place, the oversize being delivered across the air gap and being able to cross the gap centrifugally for further grinding.

The air gap provides air separation or classification. By adjusting the effective width of the gap or by adjusting the height of the plate 51 and the screen 63, or by varying the extension of the ring or apron 61, over the gap, the relationship of the centrifugal urge to the rate of flow or effectiveness of flow of air through the air gap can be varied. The narrower the gap, the finer the product. This control is critical.

The screen ring 54 in the air gap is used to prevent the escape of the charge of balls or of substantially oversize particles when the mill is running slow or is at rest. Qther means may be employed for the same purpose.

In the use of the device I have found a speed of approximately 35 ft. per second to be satisfactory, but this speed can be varied. Where the inside diameter of the grinding chamber is from 47 to 48 inches, a speed of approximately 160 R. P. M. is satisfactory. It will be understood that all of these factors may be widely varied. The size of the balls may also be varied. I may use balls of various sizes from in diameter up, and a charge of balls of mixed diameter. It will be understood that the charge may widely vary. However, a typical charge, in a machine which I employ includes five hundred pounds of balls divided as follows: i

100 lbs. in diameter 200 lbs. A" in diameter 150 lbs. in diameter 50 lbs. in diameter This is merely illustrative, as the size and distribution of size of the balls of the charge may be widely varied.

I thus provide an efficient structure and method in which attrition grinding and impact grinding are combined with air separation. The result is a highly eflicient method and structure, which is economical in power and in metal, and which has a high capacity. The device is compact, and employs a minimum floor space.

I claim:

1. In a ball mill, a vertically axised rotor and means for rotating it, said rotor including a circumferentially extending flexible side wall, a charge of balls adapted to travel with said side wall during normal rotation of the rotor, means for delivering the material to be ground for mixture with said balls, a normally fixed impacting member located within the space surrounded by said wall and means for flexing said wall and for thereby directing inwardly against said impacting member the mixed mass of balls and material undergoing crushing.

2. In a ball mill, a rotor and means for rotating it, said rotor including a circumferentially extending flexible side wall, a charge of balls adapted to travel with said side wall during normal rotation of the rotor, means for delivering the material to be ground for mixture with said balls, a normally fixed impacting member located within 10 the space'surrounded by said wall and means for flexing said wall and.for thereby directing inwardly against said impacting member the mixedmass of balls and material undergoing crushing.

3. The structure of claim 2 characterized by and including multiple means effective simultaneously to flex the flexible side wall inwardly at a plurality of points about its circumferential pa h.

4. The structure of claim 2 characterized by and including a plurality of rollers positioned and adapted simultaneously to flex the flexible side wall inwardly at a plurality of points about its circumferential path;

5. In a ball mill, a rotor and means for rotating it, said rotor including a circumferentially extending flexible side wall, a charge of balls adapted to travel with said side wall during normal rotation of the rotor, means for delivering the material to be ground for mixture with said balls, a normally fixed impacting member located within the space surrounded by said wall and means for flexing said wall and for thereby directing inwardly against said impacting member the mixed mass of balls and material undergoing crushing, and means for preventing the escape of the charge of balls efiective during slowing or stoppage of the rotor.

6. In a ball mill, a vertically axised rotor and means for rotating it, said rotor including a, circumferentially extending flexible side wall, a charge of balls adapted to travel with said side wall during normal rotation of the rotor, means for delivering the material to be ground for mixture with said balls, a normally fixed impacting member located within the space surrounded by said wall and means for flexing said wall and for thereby directing inwardly against said impacting member the mixed mass of balls and material undergoing crushing, and means for preventing the escape of the charge of balls efiective during slowing or stoppage of the rotor, including screen means in the line of escape of ground material from the rotor.

'7. In a ball mill, a rotor and means for rotating it, said rotor including an inwardly concave side wall of yielding material, means for centrifugally delivering material to be ground to the'concave interior of said side wall, a normally fixed impact member located in the space surrounded by said side wall and means for causing a movement of the material against said impact member, including a roller opposed to the exterior of said side wall and adapted to cause an inward flexure of said side wall.

8. In a ball mill, a rotor and means for rotating it. said rotor including an inwardly concave side wall of yielding material, means for centrifugally delivering material to be ground to the concave interior of said side wall, a normally fixed impact member located in the space surrounded by said side wall, means for causing a movement of the material against said impact member, including a roller opposed to the exterior of said side wall and adapted to cause aninward flexure 01' said side wall and means for adjusting said roller toward and away from the axis of said rotor.

9. In a ball mill, a rotor and means for rotating it, said rotor including a side wall against which the material to be ground is centrifugally held during rotation of the rotor, a normally fixed impacting member mounted within the space surrounded by said side wall, means for directing the material to be ground from said side wall against delivered material to be ground, another portion being positioned in the line of delivery or the impacted material as it leaves said first portion.

10. In a ball mill, a rotor and means for rotating it, said rotor including a side wall against which the material to be ground is centrifugally held during rotation of the rotor, a normally fixed impacting member mounted within the space surrounded by said side wall, means for directing the material to be ground from said side wall against said impact member, said impact member including a plurality of angularly related portions one of said portions being positioned to receive the delivered material to be ground, another portion being positioned in the line or delivery of the impacted material as it leaves said first portion, and third portion in the line of delivery oi the impacted material from the second portion.

11. In a ball mill, a rotor and means for rotating it, said rotor including a side wall against which the material to be ground is centriiugally held during rotation of the rotor, a normally fixed impacting member mounted within the space surrounded by said side wall, means for directing the material to be ground from said side wall against said impact member, said impact member including a plurality of angularly related portions one of said portions being positioned to receive the delivered material to be ground, another portion being positioned in the line of delivery of the impacted material as it leaves said first portion, and means for adjusting said impact member toward and away from said side wall, eflective while the rotor is rotating.

1-2. In a ball mill, a base, a central post, a rotor and means for rotating it about an axis coincidental with said post, said rotor including a side wall against which the material to be ground is centrifugally held during rotation of the rotor, an impacting member located within the space surrounded by said side wall, and mounted on said post, means for directing the material to be ground from said side wall against said impact member, and means for feeding the material to be ground toward said side wall.

13. In a, ball mill, a base, a central post, a rotor and means for rotating it about an axis coincidental with said post, said rotor including a side wall against which the material to be ground is centriiugally held during rotation of the rotor, an impacting member located within the space surrounded by said side wall, and mounted on said post, means for directing the material to be ground from said side wall against said impact member, and means for feeding the material to be ground toward said side wall, including a hollow portion of said post having an outwardly extendin feed discharge a erture, said rotor having a floor portion adapted to receive said material.

14. In a combined grinding and classifying device i'or fine materials, circumferentially extending flexible conveyor ring, a generally horizontal plate, means for rotating said ring and plate in unison about a generally vertical axis, at a speed effective to feed material centrifugally outwardly across said plate and to hold the material centrifugally against said conveyor ring for movement therewith, a discharge ring associated with said plate and adapted to deliver toward said conveyor ring the material delivered to said plate, said ring having a circumferential outer discharge edge. a generally horizontally extending separating ring having a tree inner edge radially spaced outwardly from said discharge edge and separated therefrom by a gap, adapted to deliver to the conveyor ring the material which crosses said gap, means'for maintaining a flow of air through said gap, an impact structure positioned within said conveyor ring, means for fiexing said conveyor ring and for thereby delivering particles for impact against said impact structure, said plate being positioned and arranged to receive the crushed material and to direct it centrifugally outwardly across said gap to said conveyor, the width of said gap, in relation to the speed of centrifugal delivery of particle across said gap and the rate of air flow through the gap, being arranged to maintain a predetermined classification by fineness, between particles crossing said gap and particles escaping through said ap 15. The structure of claim 14 characterized by and including a screen overlying said plate and adapted to prevent the delivery of oversize particles to said plate.

16. The structure of claim 14 characterized by and including means for bypassing oversized material, said means being adapted to deliver oversize material to the conveyor ring for regrinding.

17. The structure of claim 14 characterized by and including bypass means adapted to segregate the oversize particles from the fine particles and to direct said oversize particles to the conveyor ring for regrinding.

18. In a combined grinding and classifying device tor fine materials, a circumferentlally extending conveyor ring, a generally horizontal plate, means for rotating said ring and plate about a common and generally vertical axis, at speeds efi'ective to feed materials centrifugaliy across said plate toward said ring, and to hold the material centriiugally against said ring for movement therewith, said plate having a discharge ring with a. circumferential outer discharge edge, a generally horizontal separating ping, associated with said conveyor, said ring having a sharp, inwardly directed lip spaced radially outwardly from said discharge edge and lying in a predetermined plane, means for maintaining a flow of air through the gap between the opposed edges of said rings, an impact structure positioned within said conveyor and means for directing the particles from said conveyor against said impact structure and for thereby impacting them, said plate being positioned and arranged to receive the crushed material and to'redirect it centrifugally outwardly toward said conveyor,

RE ERENCES CITED The following references are 01' record in the file or this patent:

UNITED STATES PATENTS Y Number Name Date 318,181 Grimn May 19, 1885 352,459 Fuller et al Nov. 9, 1886 429,679 Duc June 10, 1890 (Other references on following page) UNITED STATES PATENTS Number Name Date Clarkson Sept. 8, 1891 Sackett Aug. 21, 1906 Ernst Dec. 7, 1909 Emerick July 12, 1910 Penfleld Nov. 8, 1910 Fuller Oct. 1, 1912 Koch Nov. 9, 1920 Sturtevant Sept. 13, 1921 Kreutzberg Jan. 15, 1924 Kreutzberg' Jan. 20, 1925 Hildebrandt Nov. 2, 1926 Number Number Germany Oct. 28,1931

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