US2433872A - Gyratory impact ball mill - Google Patents

Description

Jan; 6, 1948. .`G. sYMoNs GYRATORY IMPACT BALL MILL 5' Sheets-Sheet 1 Filed Jpne 16, 1944 f E. N Q v. no. .8 ....o .Wm SQ mw Q m TN 6.,.. www ,ZM a my .50M .MP j@ Jan. 6, 1948. l.. e. sYMoNs GYRATORY IMPACT BALL MILD Filed June 16, 1944 5 Sheets-Sheet 2 Ivre?? 6. J was y KJ Jan. 6, 1948..

L. G. SYMONS GYRATORY IMPACT BALL MILL Filed June 16. 1944 5 Sheets-Sheet 3 I?? yen for .Zaren @..Symms gf P 4 c-Am Patented Jan. l6, '1948 f om'roar IMPACT Bau. una. vLoren G. Simons, Hollywood, Calif., assignor to 'Nordberg Manufacturing Company,

Milwaukee,

' Wis., a corporation of Wisconsin Ambition une 16, 1944, Serial N0. 540,628 l 15 claims. (ci. en -175) My invention relates to an improvement in gyratory impact ball mills and has for one purpose to provide an improved mill for reducing relatively small particles to substantially ner size.

Another purpose is to providefa gyrating ball mill in which balls or similar members are bodily upwardly tossed, with the material to be reduced, and are again impacted after free travel and fall under gravity. l

Other purposes willl appear from time to time in the course of the specification and claims. My copending application Serial No. 540,629, flied June 16, 1944, contains method claims covering a method of fine reduction which can be carried out by the present structure.

I illustrate the invention more or less diagrammatically in the accompanying drawings, wherein: I

l Fig. 1 is a vertical axial section;

Fig. 2 is a section on line 2-2 of Fig. l;

Fig. 3 is a section on line 3-3 of Fig. i; and

Fig. 4 is a diagram.

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

Referring to the drawings: i generally indicates any suitable base structure herein shown as a plurality of I-beams, which may be mounted'on any suitable foundation. Y

2, 2 are any suitable cross supports connecting the I-beams I, I.

3 is any suitable bearing sleeve mounted onu one of the I-beams I and provided, for example, with a supporting bracket I.

Within the sleeve 3 are positioned suitable antifrictlonal bearing assemblies 3, 5, in which rotates Mounted between the I-beams I and in communication with the inner end of the bearing sleeve 3. is a housing including an upper sleeve 9, with a flared and generally conic lower portion I0. Connected to the lower portion I0 is the bottom housing element II, the parts being secured together, for example, by bolts I2. The bottom member II is provided with a central bottom sleeve I3 in which is positioned any suitable antifrictional assembly I4, which receives` the shaft generally indicated as I5. Keyed on the shaft, within the housing formed by the members 9, I0 and II, is the gear I6, in mesh with the drive pinion I1 at the inner end of the shaft 6. Thus,

.mill in which there is a minimum of wear or grinding or abrasion of the wearing parts.

rotation of the shaft Bthrough the pulley 1, ro-

tates the gear I6 and the shaft I5. 'I'he shaft I8.' 'I'he needle bearing assemblies 2| center and rotatably support the shaft in relation to the housing sleeve 9. Mounted on the upper end of the housing sleeve 9 is the spherical bearing ele- Y ing with a partial upper closure 3|, having a a drive shaft 6, provided withv an exterior drive pulley l, about which pass any lsuitable drive belts 8, which extend to any suitable vdriving member. motor or the like. not herein shown.

central aperture 32. 33 is a bottom, annular closure member for the housing 30. At its inner edge it is secured to the generally conic sleevel portion 34, which is shown as secured to or integral -with a central upwardly extending sleeve portion 35, outwardly onset as at 36, and terminating in a generally cylindrical upper end portion 31-with securing lugs 38. The sleeve portion 31 partially surrounds the fixed support 23. Secured to it is an upper structure which includes a bottom securing flange 33. an upwardly extending generally cylindrical sleeve 40, and an inwardly extending element I which surrounds and positionsal bearing member 42. The bearing member I2 has a downwardly concave generally spherical bearing surface engaging and conforming to the upwardly convex bearing surface of the member 23. It is provided also withoil inlet apertures 43 out of line with the member 4I. 44 is. abottom,y confining angle ring, which assists in clamping the outer edge of the flexible seal ring 45. The inner edge of the ring 45 is clamped in any suitable manner to the sleeve 9. It is shown as held in position by a downwardly extending portion of the fixed supporting member 23. Note Ythat the member 9 is provided with one or more oil ducts 46 in communication with oil ducts or spaces 41, whereby the space within the sleeve 9 communicates with the space above the flexible ring 45. It will beA understood that the flexible ring may be made of any suitable oil resisting material, -such as a synthetic or a rubber substitute. Oil may thus pass through the apertures 43 and across the opposed spherical surfaces and finally through the ducts 46 and 41 to the interior of the sleeve 9, and thence downwardly through the bearing assembly I4. Note also the supporting bearing assembly I4a about the shaft I5 and below the gear I6, whereby downward endwise movement of the shaft I5 and its associated parts, in relation to the housing members 9, I and II, is prevented.

The upwardly extending sleeve 40 may be provided with any suitabe cover. but I illustrate an upwardly convex and generally cylindrical member 59. -which serves as a feed receiving and feed limiting element and is shown as at all times underlying any suitable feed spout I, which may be set or adlusted, by means not shown herein, to any suitable vertical or radial distance from the upper spherical surface of the member 59. It will be understood that the material fed to the mill flows through the spout 5I and passes over the surface of the feed limiting member 50 until it drops downwardly through the aperture 32 and thus into the interior of the housing 30.

The housing 30 is gyrated by the rotation of the shaft I5 and its eccentric arm IB. The center of this gyratory movement is indicated as X in Fig. 1, which is the center about which the spherical surfaces of the members 23 and 42 are described. I may also describe the upper surface of the member 50 about the same center, although this may not be essential. A

The eccentric arm I8 on the shaft I5 terminates in a generally cylindrical portion 80, which is surrounded by any suitable anti-.frictional bearing' structure 6I. 62 is an outer and generally cylindrical sleeve, which is connected by any suitabe sealing or inter-penetrating connection with the member I8. I illustrate for example a circumferential channel 64 in the member I B. 65 is an oil duct through which oil can flow from the space Within the housing members 9 and I0 through the bearing assembly I5 to the bearing assembly 6I and thence to the space 63 within the sleeve B2. 61 is any suitable bottom closure or plate for the sleeve 62. 68 is a supporting member which is secured in relation to the sleeve 62 and the bottom plateA 61 by any suitable securing means 69. At its upper edge it is secured, for example, by bolts 69a to the lower edge of the member 34 and to the bottom portion 33 of the gyrated mill housing 30.

I provide inner wear taking members in the housing 30. I illustrate, for example, a bottom plate or ring, including an inner and slightly conic portion 10, which may be provided at its inner edge with a separately removable and replaceable ring 1I, which denes an inner discharge outlet space 12. Extending about the member 35 are removable sleeve elements 13, which may have upper portions 14 extending about and protecting the angle or offset 36 of the member 35. 'I'he member or members 13' may also include an outlet chute portion 15, with ts conic collecting ring 15a, which discharges into any suitable material receiving member, not herein shown. The member 10 also includes an outer rim or wall portion 16, I`hown as inclined somewhat outwardly from the outer edge of the member 10. The bottom member thus formed mayV include a portion 11, which abuts against vthe -bottom plate 33 of the housing 30.` An upper and separately removable sleeve or liner 1B extends upwardly from the upper edge of the member 16. It will be understood that the details and yconformation of these various wear taking elements may be widely varied, and I provide wear .taking lining members which may be removed in any suitable manner from the interior of the gyrated mill housing 30. It will be noted, for example, that the top closure ring 3l of the housing 30 is provided with removable securing means including lugs on the housing 30, lugs 8I on the ring 3l and connecting screws 82. Thus, ready access may be had to the interior of the member 3D for insertion or removal of the wear taking members. It will be understood, of course, that the members 13 may be made in a plurality of segments for easy insertion and re moval. Note also that the inner diameter of the member 'IIJ is suicient to permit it to clear the members 31 and 14.J The ring 'Il is preferably made segmental, for ready removal. In order to confine thehousing 30 and its associated parts to gyratory movement, and to prevent its bodily rotation, I provide a flexible connection between it and to the fixed portions of the device.

Referring to Fig. 2, I illustrate a bracket extending upwardly from one of the I-beams I. Connecting the upper portion of the bracket 99 with the side of the gyrated housing 30, I illustrate a fiexure permitting link structure. It includes a double faced abutment element 9| on the member 90 and a similar double faced abutment element 92 on the housing 30. Extending between these abutments is a link structure which includes two compression members or bolts 93. Each bolt carries a spacer 94, against each end of which are positioned clamping abutments or plates 95. Compressed between each such plate and the opposed face of one of the abutments 9| or 92, is a mass or body of flexible distortable material 96, such as rubber or a rubber substitute. At each end of the compression members 93 is an outer abutment plate 91. Between each such plate 91 and the opposed face of the abutment 9i or 92, is another mass 98 of rubber or any suitable rubber substitute.

It will be seen that the structure thus provided prevents rotation of the mill housing 30, but does not interfere with its gyration about the center X.

I may provide any suitable lubricating means. I illustrate, for example, theroil pipe |00 which extends from the bottom plate 61 to the interior of the sleeve 40. The oil may be circulated by any suitable means, such as the gear pump IDI.

It will be realized that whereas I have described and shown a practical and operative device, nevertheless many changes may be made in size, shape, number and disposition of parts. I therefore wish my drawings and description to be taken as in a broad sense illustrative and diagrammatic rather than as limiting me to my specific showing herein. It will be understood, for example, that the details of the drive structure may be widely varied, that the shapes and contours and proportions of the various parts may be Widely varied, and that various feeding means,

tially in size, shape and material.

known in the art, maybe employed to feed material to the mill and to limit the feed.

The use and operation of the invention are as follows:

I show, broadly, a, grinding mechanism for .reducing relatively small particles to still smaller v size, a mechanism which is broadly in the ball mill iield and does work at the stage at which ball mills are currently employed. In the use of the device herein shown, I gyrate a bowl or plate, such as 10, 16, about a center located somewhat above the bottom of the plate. The elevaline a chamber in which the particles are ground.

The material to be ground may be fed down the spout I to the upper spherical surface of the distributor 50. 'I'he material then drops through the top feed aperture 32 and mingles with the impacting members,-or balls, illustrated at H0 in Fig. 1. It will be understood that I may employ a wide variety of small impacting elements, balls, pebbles, or the like. They' may differ substan- They must, however, be of proper size, shape and material to serve as impacting or reducing members between and against which the material to be crushed is reduced. I may even employ a plurality of loose rings surrounding the central supporting structure and formed with a variety of diameters.

In any event, whatever specific type or form of impacting members may be employed, I build up a mixed mass in the impacting chamber dened l by the above mentioned elements 10, 'l5 and 18,

and subject this mass to a series of impacts re- 1 sulting from the rapid gyration of the bowl or plate structure. y A

The operation of the device may be understood in connection with the diagram, Figure 4, in which chine it is important that the length of stroke and the speed of stroke thus imparted to thel bowl are such that the balls or impacting members, and the large particles undergoing grinding,

' are thrown upwardly from and by the bowl, at

the end of the upward movement of the bowl at B,.far enough and high enough so that when the balls or impacting members and the particles amava contact and are contacted by the bowl. The force livered by the bowl. In eilfect, I obtain a multiple impact, because the mass of balls and particles separate out or scatter on the upward and downward stroke. This eect is particularly marked if the machine is operated wet, with water supplied to the interior of the impacting chamber.

. The final or bottom particles are struck iirst and members.

the result is an instant and complete reversal of direction of movement oi' the particles and impact These, in turn, lare carried upwardly to impact the still falling upward part of the mass. This action is entirely unlike anything found in prior art ball mills, and involves a multiplication or sequence of impacts at a single movement of the bowl. Each ball or impact member, which has'just changed its direction of movement, will strike againstthe mass vabove it just as hard as did the bowlk itself. This is necessarily so because it is now traveling in reverse direction at -the same sp'eed as the speed of travel of the bowl.

The mass of the bowl is so great, in relation to the mass of any individual particle or impacting member, that it is not perceptibly slowed down by the successive impacts against individual im-l pact members and it continues to multiply its breaking eilect by carryingv the already impacted members andparticles upwardly against the still downwardly falling balls and particles. As a result, the theoreticalslowing down ,of the bowl or plate by its impact against the particles and impacting members is unimportant. It is a simple matter so to relate the length and the speed of gyration under load as to obtain the desired impacting eiTect.

Afurther characteristic of the structureherein shown is the 'classication or separation of materials` by size, which takes place during the use of the apparatus. Especially when run wet, the machine automatically sizes the material undergoing grinding, because the small particles do not travel upwardly as fast as the large particles.

fall, they do not contact the surface of the bowl until the bowl has again been down to its lowest level, as at A, and is advancing upwardly to an intermediate level near C. It.is at C, at the intermediate position, that the rising portion of the bowl is traveling -at its fastest. When the bowl is traveling upwardly, between A and C, it will contact the downwardly falling particles and impacting members after they yhave received a substantialdegree of gravital acceleration. The re- 'sult is an impact of maximum effect. It should violent impact when the balls or impact elements They lag behind and, in eiect, in the course of each upward movement of the mixed mass of material, the flne particles are concentrated in the space just above the top of the plate or bowl, while the impacting elements and the larger particles travel upwardly a greater distance. As the mass then drops downwardly toward the plate, a piston action takes place and the fines tend to be moved inwardly and upwardly along the slope of the truncated conic portion 10. Eventually thennes pass out through the discharge aperture 12 and may be received by the spout 15 and delivered to any suitable receiving area or member. The conic ring 15a deilnes a receiving area along which the iines ilow to the spout. l f

An important characteristic vof my apparatus is that the downward withdrawal of the impacting member vorbowl from below the xmass of material subjects the mass to a degree of suction from below, and causes a separation` and downpiston toward the' impacting bowl. As the mass falls and the bowl rises, thispiston eect tends to expel the line particles inwardly toward the central discharge aperture. The coarser particles respond less readily to the above described suction and piston action and are retained in the grinding zone until properly reduced.

A feature of the operation of my device which. is important is the employment of the outer part of the grinding zone within the bowl and bowl housing to grind or reduce the particles, and the employment of the inner or central partrof the zone of treatment as a separating and conveying or delivery zone. The amplitude of impacting stroke is progressively reduced from the periphery of the bowl to the discharge opening, as the particles approach the center about which the bowl is gyrated. It should be kept in mind that the method may be carried out either wet or dry.

The slope of the bowl bottom insures the avoidance of glancing blows against the impacted mass, and prevents undue wear on the bowl bottom. The material is outwardly as well as upwardly thrown, and will pile up higher at the outer edge, due to the central upward slope of the bowl bottomand the relative position of the center of gyration to the bowl bottom. This slope will cause the mixed mass to pile up higher at the outer edge and intermediate area of the bowl. In prac- I tice, the major portion of the load, or of the mixed mass, will be thrown clear of the surface of the bowl, and will thereafter` fall freely under gravity until again impacted by the bowl. Only the thin central portion of the material will ride up and down with the bowl. This central portion or layer will move substantially continuously on the bottom of the bowl, but there will be plenty of action effective to keep the lines moving through to the discharge outlet. The impacting members will tend to remain in the outer part of the zone of treatment, and will not generally ride up across the central slope to the dischargeoutlet. I find lt eiective to control the length and frequency of stroke in such fashion as to control the grinding action which takes part in the outer portion of the bowl, in order to maintain maximum results. The inner part of the bowl area or zone of treatment provides an ideal classifying action. In practice, a light layer of agitated material in the center of the zone of treatment, and around the discharge outlet, acts as a three dimensional screen and prevents oversize from splashing or ilying to the center of the zone of treatment without being subjected to a classifying action. The slope of the central part of the bowl can be widely varied in order to control the-relative position or contour of the material inside the bowl.

In discussing the operation, I have considered the ball mill action as an impact action against a body or charge of material. While, in terms of broad method, I could bodily impact the entire mass or charge simultaneously, in the use of the invention according to the drawings of the present application I have introduced a movement that limits the volume of the charge which is under impact at any one time. Limiting the amount of material impacted at one time also limits the strain to which the machine is at any one time subjected. In practice it is advantageous to limit the amount of material simultapacting member or zone. If I assume. referring to Figure 4, that the impact takes place approximately half way between A and C, then only one eighth of the'bottom of the bowl will at any instant have material in contact with it that is be- -ing accelerated. The rest of the bowl area will not be under strain, as the material will be clear of the bottom of the bowl. In other words no more than one eighth of the circumference of the bowl is performing work at the same time. And the zone of simultaneous strain is moving rapidly around the bowl, so that no part oi the bowl is subjected to a continuing strain due to impacting the charge. While this may not be necessary for the practice of the invention, it is helpful in connection with the design and employment of commercially acceptable machines for carrying out the invention.

It will be understood that the present invention may be employed in both wet and dry grinding. In the former case the free fall of the material after impacting will be impeded. However, where the term is used in the claims it will be understood to mean that, so far as the machine itself is concerned, the particles have a substantial travel downward preceding the ensuing impact, during which travel they are not supported by the bowl. Similarly, when the charge is falling, in wet-grinding, the piston action emphasized in the last amendment, is somewhat modified by operating with water instead of air as a iluid medium, but substantially the same result is obtained. In connection with the characteristic "bodily elevating of the mass, it will be understood that it is notl meant that the entire contents of the mill are simultaneously elevated, but that there is a bodily elevation 0f that part of the mass which has just undergone impact. This zone of bodily elevation moves progressively around the mill, in very rapid succession. In either event, the bodily impacting and lifting of that part of the mass which is in the impacting zone is a very different action than a mere agitation of the mass, or a tumbling of the mass, such as is characteristic of prior art grinders. ball mills and the like.

I claim:

1. In a grinding and classifying mill, an impasting bowl mounted on an inclined axis for .gyration about a center located above the bottom of the bowl, said bowl having a bottom in the form of 'a truncated cone, the truncated apex of the cone dening a discharge aperture surrounded by said conic bottom, said bowl having an outwardly flared circumferential wall upwardly extending from the lower outer edge of said conic bottom, a plurality of movable impacting elements loose in said bowl, means for delivering the material to be ground to the interior of said bowl, and means for gyrating said bowl through an excursion of suiiicient vertical amplitude, speed and frequency to throw a substantial proportion of the mass of material to be ground, together with the impacting elements associated therewith, upwardly clear of the bottom of the bowl, at each upward gyration of the bowl bottom, said bowl being adapted to receive said mass of material when it drops, the mass of the bowl being substantially greater than the mass of the material which is simultaneously received by the bowl at any one time.

2. In a grinding mill, an impacting bowl mounted on an inclined axis for gyration about a central point, said bowl having a bottom with a generally central discharge aperture, said bowl having a circumferential wall upwardly extending from the outer edge of said bottom, a plurality of movable impacting elements loose in said bowl, me'ans foi-,delivering the material to be ground to the interior of said bowl. and means for gyrating said bowl through an excursion of sulcient vertical amplitude, speed and frequency to throw a.. substantial proportion of the mass of materiall to be ground, together with the impacting elements associated therewith, upwardly clear of the bottom of the bowl, at each upward gyration of the bowl bottom, the bowl being adapted to receive said masslof material when it drops, the mass of the bowl being substantially greater than the mass of the material which is simultaneously received by the bowl at any one time.

3. In a grinding mill, an impacting bowl mounted on an inclined axis for gyration about a central point, said bowl havinga bottom with a generally central discharge aperture, said bowl vhaving a circumferential wall upwardlyextending from the outer edge of said bottom, aplurality ofA movable impacting elements loose in said bowl, meansl for delivering the material to be ground to the interior of said bowl, and means for gyrating said bowl through an excursion of sumcient vertical amplitude, speed and frequency .to throw that part of the material to be ground, together with the associated impacting elements, which is'opposed to the outer portion of the bowl Y bottom, upwardly clear of the bottom of the bowl at each upward gyration of the bowl'bottom, while causing a relative movement of the particles on the inner part of the bowl surface toward the central discharge aperture, the bowl being adapted to receive the mass of material when it drops, the mass of the bowl being substantially greater than the mass of the material which is simultalneously contacted at any time by the bowl.

4. In a grinding mill, an impacting bowl mounted on an inclined axis for gyration about a central point susbtantially above the bowl bottom, said bowl having a bottom with a generally central discharge aperture, a supporting structure for said bowl extending upwardly throughV said discharge aperture, said bowl having a circumferential wall, upwardly extending from the outer edge of said bowl bottom, a plurality of movable impacting elements loose in said bowl,

means for delivering the material to be ground to the interior of said bowl, said meansincluding a feed discharge plate movable unitarily with said bowl and located `substantially above said center, and means for gyrating said bowl through an excursion of sufiicient vertical amplitude,

speed and frequency to throw that part of the material to be ground, together with the associated impacting elements, which is opposed to the outer portion of the bowl bottom, upwardly clear of the bottom of the bowl at each upward .-Jgyratio'n of the bowl bottoni, the mass of the bowl being substantially greater than the mass of the material which is simultaneously contacted at any onetime by the bowl.

5. In a grinding mill, an impacting bowl Amounted on-an inclined axis for gyration about a central point, said bowl having a bottom with a generally central discharge aperture, a plurality of movable impacting elements in said bowl, means for delivering thematerial to be ground to the interiorof said bowl, and means for tilting and gyrating said bowl about said central p'oint, thrcugh an excursion of sumcient vertical amplitude, speed and frequency to throw a substantial proportion of the massv of material to be ground together with its associated impacting elements,

upwardly clear oi the bottom of the bowl at each I bowl.

6. In a grinding mill, an impacting bowl mounted for gyration about a central point, said bowl having a bottom with a generally central discharge aperture, a plurality of movable impacting elements in said bowl, means for delivering the material to be ground to the interior of said bowl, and means fortilting and gyrating said bowl about said central point, through an excursion of suillcient vertical amplitude. speed and frequency to throw substantially the entire impacted mass of material to be ground together with the impacting elements included therewith, upwardly clear of the bottom of the bowl at each upward gyration of the bowl, said bowl being adapted to receive said mass of material when it drops, said tilting and gyrating means being adapted `to time the movement of thebowl to cause the bowl to meet the falling material at any'given point about thebowl, when the bowl is moving upwardly, ,the mass of the bowl being substantially greater than the mass which is simultaneously received by the bowl at any one time.

7. In a une grinding mill. a bowl mounted on an inclined axis for gyration'about a predeter-v mined center, said bowl having an outlet located adjacent its center, and 'having a bottom portion and a circumferential side portion upwardly extending from the periphery of the bottom portion, a plurality of impacting members located within and movable .in relation to the bowl, and movable in relation to each other, means for delivering material to be ground tothe interior of the bowl and means for gyrating said bowl about its center of gyration through an excursion of sufficient vertical amplitude, and atsufiicient linear speed, to carry the bowl and the mixed mass of impacting members and particles undergoing grinding rapidly upwardly on the up stroke, and to withdraw the .bowl from supporting relationship with a substantial proportion of said mass, on the vdown stroke, whereby the mass is .permitted to fall freely under gravity-until again caught by the bowl'on the up stroke, the mass'of the bowl ferential wall, upwardly extending from the outer edge of said bowl bottom, a plurality of movable impacting elements loose in said bowl, means'for delivering the material to be ground to the interior of said Ibowl including a feed discharge plate movable unitarily with said bowl and located substantially above said center, and means for gyrating said bowl through an excursion of suillcient vertical amplitude, speed andfrequency to throw that part of the material to be ground, together with the associated impacting elements, which is opposed to the outer portionof the bowl bottom, upwardly clear of the bottom of-the bowl at each upward gyration of the bowl bottom, the

- 11 mass oi the bowl being substantially greater than the mass of the material which is simultaneously contacted at any one time by the bowl.

9. In a grinding machine, a bowl and means for mounting it for gyration about a center located above the bottom of the bowl. a plurality of small, relatively movable grinding elements positioned in said bowl, means for feeding to the bowl, for mixture with said grinding elements, the material to be ground, and means for moving the prolongation of the axis of the bowl beyond said center of gyration through a circular path and for thereby imparting to the bowl itself a tilting wobble or sufficient vertical amplitude to toss a portion of the charge formed of said material and grinding elements free from the bottom of the bowl in a limited area oflift which advances progressively and continuously circumferentially around the bowl, and for so timing said wobble that the upwardly projected material when it falls, again contacts a part of the bowl which is upwardly rising when it strikes the previously tossed material, the mass of the bowl being substantially greater than the mass which is simultaneously received by the bowl at any one time.

10. The structure of claim characterized by and including a frame on which said bowl is movably mounted, and means for preventing rotation of said bowl, including a connecting elev ment extending between said bowl and said frame and adapted to serve as a compression-tension member, and exible connectingy means interposed between one end of said connecting element and the bowl between the opposite end of said connecting element and the frame.

11. The structure of claim 5 characterized by and including an actuating means for said bowl including a shaft mounted for rotation about a generally Vvertical axis, means for rotating said shaft,l and an actuatingconnection between said shaft and said bowl adapted to impart gyration to said bowl in response to rotation of said shaft, including an eccentric element on said shaft and a rotatable connection between said eccentric element and said bowl, the axes of said shaft and of said rotatable connection being inclined in relation to each other and intersecting generally at the point about whichthe impacting bowl is gyrated, said point being located above the bottom of the bowl.

12. The structure of claim 5 characterized by and including means for supporting said bowl including an upwardly extending support, extending upwardly through the generally central discharge aperture of the bowl, and a ball and socket bearing connection between said upwardly extending support and the bowl including opposed generally spherical surfaced members gen- 12 erally concentric with the central point 'about which the bowl is gyrated, one such.' member being ilxed and upwardly convex, theother moving with the bowl and being dowwardly concave. 13. The structure of claim 5 characterized by land including a support for said bowl extending upwardly through said generally central discharge aperture, and a bearing connection between said support and said bowl concentric with the central point about which said bowl is gyrated.

14. In a grinding mill a laterally extending impact plate mounted on an inclined axis, housing members associated with the plate for delining an impacting chamber, a plurality of impacting elements movable in said chamber, means for deiiveringthe material to be ground to the interior of the chamber, means for gyrating said plate and for thereby moving it upwardly and downwardly with a circumferential wave motion, through an excursion of suficient vertical amplitude, speed and frequency to throw a substantial proportion of the material to be ground, together with the associated impacting elements, bodily upwardly from the upper surface of the plate, at

an area which progressively moves about the plate, the mass of the plate being substantially greater than the mass of the material which is simultaneously received by the plate at any one time, said plate having a generally central discharge outlet spaced inwardly from the outer edge of the plate.

15. The structure of claim 14 characterized by and including an impact plate having a central aperture, and a support for said impact plate extending into said central aperture, said support defining, with said discharge outlet, a discharge slot through which the reduced material may pass.

LOREN G. SYMONS.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date l' 1,213,264 Ropes Jan. 23, 1917 13,892 Vose Dec. 4, 1855 2,144,145 Daniel Jan. 17, 1939 '706,102 Pendleton Aug. 5, 1902 FOREIGN PATENTS Number Country Date 361,992 Great Britain Dec. 3, 1931 802 Great Britain 1895' 180,743 Switzerland Nov. 15, 1935 331,540 Germany Jan. 11, 1921

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