US2124127A - Screen unit for ball mills - Google Patents

Description

J. SEROY July 19, 1938.

Filed Sept. 29, 1934 2 Sheets-Sheet l w R N m m m b 0 m. R x 3 Q V mm N N INVENTOR W y m m .J

July 19, 1938. J. SEROY 2,124,127

SCREEN UNIT FOR BALL MILLS Filed Sept. 29, 1934 2 Sheets-Sheet 2 INVENTOR JOIZJZ/ Seroy I ATTQRNEY Patented July 19, 1938 UNITED STATES PATENT OFFEE SCREEN UNIT FOR BALL MILLS John Seroy, Stockton, Calif.

Application September 29, 1934, Serial No. 746,157

2 Claims.

This invention relates to mining machinery and is directed particularly to an ore grinding or pulverizing mill of that character commonly known as ball mills or cannon ball mills.

One of the objects of my invention is to provide means within the ball mill whereby all exceedingly hard and non-grindable material may be accumulated and retained from continued contact between the steel balls and the raceways.

Small exceedingly hard chips of steel from broken drills etc. often are discharged with the ore through the hopper into the ball mill. If these chips are allowed to remain in the raceways of the mill more than a few minutes they will seri- 15. ously damage the face of the raceways and probably in time damage the steel balls.

A further object of my inventionis to provide a ball mill wherein the ore is subjected to successive grinding and pulverizing actions. These successive actions upon the ore assure that it will be completely broken down into fine particles prior to passage over the amalgam plate and provides for a very effective grinding action within a compact space.

'. It is also my object to provide a sectional screen about the mill and through which the fine material passes. This screen is constructed as a sectional unit for. the reasons as will hereinafter appear.

As an additional object it is my purpose to pro- Vide an automatic control within the ore hopper of the ball mill in order that the flow of crushed ore into the hopper may be automatically controlled according to the volume of ore being ground within the mill.

A further object of the invention is to produce a simple and inexpensive device and yet one which will be exceedingly effective for the purpose for which it is designed.

These objects I accomplish by means of such structure and relative arrangement of parts as will fully appear by a perusal of the following specification and claims.

In the drawings similar characters of reference indicate corresponding parts in the several views:

Figure 1 is a sectional elevation of my improved ball mill.

Figure 2 is a top plan of the same partly broken out, and

Figure 3 is a fragmentary enlarged plan view of the screen and supporting members.

Referring now more particularly to the characters of reference on the drawings, the numeral 55. denotes a circular base plate of heavy cast'metal provided with an integral and downwardly depending supporting fiange 2. This base plate i is formed with concentric outer and inner and vertically offset grooves 3 and 4 forming raceways. These raceways are properly machined 5 and tempered in order to prevent undue wear.

Intermediate the adjacent raceways 3 and 4 is formed an upstanding portion 5 so that the top periphery of the plate outwardly of the outer race is on a level lower than said portion 5. The 10 faces of this portion 5 are a continuation of the surfaces of said raceways which are relatively deep.

Formed on the opposite side surfaces of the inner raceway 4 are endless relatively small 15 grooves 6 and 6a. These concentric grooves 5 and 6a are of course depressed in the base plate I and are for the purpose hereinafter described.

A cone 1 is formed centrally of the base plate the cone also being concentric with the raceways 20 3 and 4 and grooves 6 and 6a. The upper surface of the cone is tangent to the adjacent side of the raceway 4; the groove 6a being disposed adjacent the junction of the cone with the raceway.

Supported in the raceways are steel balls B, 25 said balls being somewhat smaller in diameter than that of the raceways. The raceway 3 is preferably provided with eleven balls, and the raceway 4 with six balls which do not fill the respective raceways, as indicated in Figure 2. 3

Supported on the balls B and in frictional engagement therewith is a circular head 8 also of heavy cast material. This upper head member 8 is formed with relatively shallow raceways 9 and I 0. These raceways 9 and ID are concentric and are formed in cooperating alinement with the lower raceways 3 and 4 respectively.

The interior surface of the head 3 extends downward some distance on the outer side of the raceway II] as at I! to a termination adjacent 4d the horizontal axial plane of the corresponding balls in order to provide a relatively narrow passage I2 between the concentric raceways.

The head 8 is provided with a central opening l3 into which the neck of a downwardly converg- 45'- ing ore feeding hopper I4, is secured by suitable means.

Secured to the periphery of the head 8 is an upstanding drum I5. This drum I5 serves as the drive pulley which may be driven as by a belt 50- I6. Mounted adjacent the periphery of the head 8 and engaging the lower portion of the drum I 5 is a circumferential splash preventing flange IT. This flange as well as the drum is secured to the head by bolts l8.

A sectional screen unit indicated generally at I9 surrounds the head 8 in spaced relation theretothe lower edge of said screen unit being supported in a peripheral recess 20 about the top of the base plate I and extending upward therefrom at an acute angle.

' This sectional screen unit I9 comprises adjacent screen sections ZI secured in place as follows:

An upper and inner band 22 circumferentially continuous is supported in spaced relation from the drum I by means of upstanding arms 23 set at their lower end in the recess 20 and extending up to connect with the band 22 at an acute angle. The above structure constitutes the inner frame work against the outer face of which the screen sections 2I are held in place by means of a lower and outer band 24 and an upper and outer band 25. These latter bands 24 and 25 are formed in semi-circular sections with ears e formed on the ends thereof-each pair of sections being adjustably secured together by bolts and thumb screws 26 joining the adjacent pairs of ears. The lower band 24 of course rests against the plate at the bottom of the recess 20 while the upper band 25 is held in place by fingers 21 which engage the upper and inner band 22 as shown. The screen sections 2| are overlapped along adjacent longitudinal edges in the direction of rotation of the head 8 as shown in section in Figure 3.

Surrounding the base plate I and extending out from flanged engagement therewith is an amalgamating plate 28 which is set on a slight slope. This amalgamating plate 28 is formed with a fluid retaining flange 29 and an outlet spillway 30 along the lower edge.

In use my improved ball mill operates as follows:

The ore is fed into the hopper I4 along with the necessary amount of water and passes through the neck of the hopper onto the cone I from whence it flows evenly into the inner raceway 4.

The head 8 is rotated relatively slow by the belt I6 driving about the pulley I5. As this exceedingly heavy head 8 rotates the steel balls B rotate as well as travel around the raceways 3 and 4. The ore entering the mill is initially ground in the inner raceway and due to the narrow overflow passage I2 no large pieces of ore can escape without being crushed. Any particles of hard non-grindable material such as pieces of steel drills entering the mill with the ore are at once forced away from the balls B into the deep grooves 6 and 6a where they remain without harm to the mill until it is cleaned. Also, due to the position of the groove 6a it will catch some of such pieces as they slide down the raceway before they reach the same.

After passing through the inner gangue it passes over the raised portion 5 into the outer raceway 3 where it is subjected to further and more thorough grinding action.

Passing from the outer raceway the gangue flows through the screen unit I9 either by centrifugal force or by gravity. The screens retain all ore which by chance escapes the mill in any substantial size and also retains any foreign matter incapable of passing through the screen. The V-shaped annular groove formed between the plate I and the lower screen band 24 serves as a catch trough for any amalgam which may have passed through the mill.

After flowing through the screen the gangue runs over the initial amalgamating plate 28 and thereafter passes through the spillway 30 for a further amalgamating process.

If, during the operation of my ball mill, one of the screens is damaged, it is only necessary to untighten the thumb screws 26 which in turn loosen the retaining bands 24 and 25. The damaged screen section is then readily removed and replaced by a new screen section. The new screen section overlaps the adjacent screen section in the direction of rotation of the head 8 and is lapped under the other adjacent screen section. The sections are thus lapped in order that the fiow of gangue will not run against a raw edge of the screen.

As the mill is operated and the ore flows through the hopper I4 into the mill, the head 8 will gradually rise up relative to the base plate I due to the congestion of ore therebetween. I make use of this movement in preventing too great congestion within the mill in the following manner:

Mounted within the hopper I4 adjacent the top edge thereof is a circumferentially tapered cam 3I. An upwardly tapering roller tappet 32 is formed on the lower end of the ore feed control rod 33said tappet 32 being adapted to cooperate with the cam 3I.

This rod is part of any well known feed control device, such for instance as that shown in Patent No. 879,581 granted February 18, 1908 to F. B. Pettingill; the oscillating roll-supporting pendent yoke 29 of the patented structure corresponding of course to the rod 33.

Thus, as the mill is operated, the feed control roll is actuated only at regular intervals due to the roller tappet 32 contacting and riding up the cam 3|. An intermittent ore feed is thereby provided.

If however the intermittent feed supplies too great a quantity of ore to the mill the head 8 will raise vertically, causing the roller tappet to only partially engage the cam or to fail to engage the cam entirely, resulting in the feed being greatly reduced or entirely stopped respectively. This result is obtained due to the action that as the head 8 raises vertically, the cam within the hopper also is raised and as the roller tappet is tapered upwardly the cam in the raised portion will only partially move the feed control or may not even move it at all. As the mill empties the head 8 of course lowers. and the cam again engages the tappet and the intermittent feed again functions.

By forming the cam within the hopper rather than on the outside of the drum I5, as is common practice, the possibility of injury to the operator by being struck by the cam' is eliminated and a more compact feed control structure as a whole is possible.

From the foregoing description it will be readily seen that I have produced such a device as substantially fulfills the objects of the invention as set forth herein.

While this specification sets forth in detail the present and preferred construction of the device, still in practice such deviations from such detail may be resorted to as do not form a departure from the spirit of the invention, as defined by the appended claims.

Having thus described my invention what I claim as new and useful and desire to secure by Letters Patent is:

1. A screen unit for a vertical axis ball mill comprising in combination, a skeleton frame extending about the mill and upstanding from the base member, sectional screen elements disposed against said frame and forming a continuous screen structure about the mill, a split band extending about said continuous screen structure adjacent the top edge thereof and adapted to be clamped about the same, and fingers projecting inwardly from the top edge of the band across the screen structure to rest on the skeleton frame whereby to prevent downward displacement of the band when the same is unclamped.

2. A screen unit for a vertical axis ball mill comprising in combination, a skeleton frame extending about the mill and upstanding from the base member, said frame including a plurality of upstanding outwardly fiat and relatively wide arms disposed in spaced relation about the mill, screen sections disposed against said frame outwardly thereof and forming a continuous screen structure about the mill, the adjacent edges of the screen sections relative to the inner faces thereof overlapping in the direction of flow of material in the mill, each of the overlapping portions being disposed immediately behind one of the relatively wide upstanding arms whereby to protect said overlapping portions from the passing material in the mill, and clamping bands extending about all the screen sections adjacent the top and bottom thereof and removably mounting the screen sections in place against the frame.

J OHN SEROY.

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