US1946511A

US1946511A - Discharge for ball mills

Info

Publication number: US1946511A
Application number: US566939A
Authority: US
Inventors: Elmer L Van Pelt
Original assignee: AMERICAN BALL MILL Co
Current assignee: AMERICAN BALL MILL Co; AMERICAN BALL-MILL Co
Priority date: 1931-10-05
Filing date: 1931-10-05
Publication date: 1934-02-13
Anticipated expiration: 1951-02-13

Description

Feb. 13, 19.34. E; VAN FELT I 1,946,511

DISCHARGE FoR BALL MILLS Filed oct. 5, 1931 :s sheets-'sheet 1 lll Clttoz mg 3 Sheets-Sheet 2 E. L. VAN PELT DISCHARGE FOR BALL MILLS Filed-Oct. 5, 1931 Feb. 13, 1934.

Feb.13,1934. A EL, VAN FELT 1,946,511

DISCHARGE FOR BALLl MILLS Filed Oct. 5, 1951 3 Sheets-Shee'l'I 3 UNITED STA Patented Feb'. 13, 1934 DISCHARGE Foa BALL MILLS Elmer L. Van Pelt, Denver, Colo., assignor to American Ball-Mill Company, Denver, Colo., a corporation of Colorado Application October 5, 1931.

13 Claims.

This invention relates to improvements in rod or ball mills of the type employed for reducing or disintegrating materials containing minerals, for example, gold or silver ores and has reference more particularly to an improved screen and discharge device.

In the grinding of ores it is customary to feed the coarse ores into a rotating cylinder having a crushing compartment in which are located l0 suitable attrition members, such as balls or rods The material is fed into the chambers through one of the trunnions on which the cylinder is rotated and leaves through an opening in the other trunnion. Interposed between the crush- 15 ing chamber and the outlet opening are a number of grates or grizzlies through which the ground ore must pass before it can be discharged from the mill.

In mills of this type it has been customary to place the grates or grizzlies transverselyof the mill and this makes it necessary to have the mill lled to the innermost opening of the grate with attrition members and ore in order to get an eicient operation. The large load carried by the .mill makes it run very heavy and therefore it requires an exceptionally large amount of power to operate it.

It is the principal object of this invention to produce a mill of the type above described which shall be so constructed that efficient grinding either wet or dry can be accomplished with a comparatively small number of attrition members and a small quantity of ore.

The above mentioned objects are accomplished principally through the simple expedient of locating the grates with their surfaces lying parallel with the axis of rotation instead of sub stantially perpendicular as has heretofore been the custom.

This invention, briey described, consists of a cylindrical shell whose two ends are closed by means of transverse heads each of which is provided with a tubular trunnion. This shell is mounted for rotation in bearings suitably supported. The interior of the shell is lined with heavy cast liners which take up the wear and at the end of these liners adjacent the head through which. the material is discharged, a number of grates or grizzlies are arranged in such a way that they form an extension of the inner surface of the liners, so that the ground material can pass directly from the surface of the liners onto the grates and after passing through the grates, the material enters a reception chamber that is connected with the outlet opening in the Serial No. 566.939

trunnion by means of passages that extend radially and through which the material can pass from the reception chamber to the discharge opening. The grates are protected against injury from the attrition members by means of 6" sector-shaped protector plates that extend radially from the center of rotation and terminate a short distance from the inner surface of the liners in such a manner that a passage is provided for the ground ore and at the same time the attrition members are prevented from entering that part directly above the grate.

Having thus briefly described the invention, the same will now be described in detail, and for 'this purpose reference will be had to the accom- 70 panying drawings in which the preferred embodiment thereof has been illustrated, and in which:

Fig. l is a longitudinal section through the mill taken on avertical plane;

Fig. 2 is a transverse section taken on plane 2 2, Fig. 1;

Fig. 3 is a section through one of the grates and through the reception chamber, taken on uneI 3, Fig. 2; 80

Fig. 4 is a perspective View, partly in section, showing one of the grates and discharge sections with the sector-shaped 'protector plate in place thereon;

Fig. 5 is a section taken on line 5 5, Fig. 4; and 95 Fig. 6 is a side elevation looking in the direction indicated by arrows 6-6, in Fig. 5.

In the drawings reference numeral 1 indicates a cylindrical shell, the ends of which are closed by transverse heads 2 and 3. Each of these heads is 90 provided with a tubular trunnion 4, that is mounted for rotation in a bearing 5 supported on the vertical support 6. Arranged around the inner surface of the shell are a number of channels 7. One end of these channels is held in place by means of the end liners 8. These liners have been shown in transverse section in Fig. l, but have not been shown in any other view because they do not form part of the invention that is claimed in this application. Liners 8 are sector-shaped and 100 their upper ends which have been indicated by reference numeral 9 project into a groove in the inner end of the trunnion. Pins 10 connect the outer edges of liners 8 to the channels in the manner indicated in Fig. 1. Secured to the inner surface of the channels are liner blocks 11 which may be made from cast iron or other suitable material. These blocks are held in place by an arrangement covered by United States patent but whiGh has not been shown because it forms no part of this invention. The space between the liner blocks is caulked with oakum so as to prevent ground material from passing through between the blocks. 'I'he space between the end liners 8 and the opposite ends of the liner blocks forms a crushing chamber within which are located suitable attrition members 13 which may be balls or rods as may be desired. The trunnion associated with head 2 is provided with a liner 14 whose inner surface is threaded and the material to be ground is fed into the crushing chamber through this opening in the direction indicated by the arrow. The opening in trunnion 4 of head 3 has a liner corresponding to liner 14, but which has a conical opening whose walls have been indicated by reference numeral 15. This opening tapers inwardly and the inner end of the liner. which has been indicated by reference numeral 16 has a plurality of radial pockets 17 that are in communication with the conical opening so that material may pass from the pockets into the discharge opening as indicated by arrow 18. Located between the head 3 and the adjacent ends of the liner blocks are grate sections 19. These sections form part of an assembly which has been shown more in detail in Figs. 3 and 4, from which it will bc seen that the grates or grizzlies are secured to a hollow member which is substantially sector-shaped. The lower end of this member is provided with a bottom having section 20- that is parallel with the axis of rotation and another section 21 that is upwardly inclined as shown most clearly in Figs. 3 and 5. The inner end of section 21 terminates in an upwardly extending portion on which one edge of the grate rests. Extending upwardly from the outer end of bottom portion 20, is a wall 22 and the edges of this wall are integral with the sides 23 and 24. Sides 23 and 24 extend downwardly and are joined to the ends of

sections

20, 21 and-22. The inner edges of walls 23 and 24 are joined by wall 25 that extends downwardly in the manner indicated in Fig. 5 and terminates in a vertical portion 26 against which the inner edge of the grate abuts. Referring now to Fig. 6, it will be seen that the grates are removably connected with the assembly and the latter is provided with grooves 27 for the reception of the ends of the grate. If a grate is broken or is to be replaced by one having diierent sized openings, this can be readily accomplished by merely withdrawing the grate in a manner quite apparent. Extending outwardly from sides 23 and 24 are lugs 28 which are perforated for the reception of bolts 29. The upper end of wall 25 terminates a short distance below the upper ends of walls 23 and 24 and the latter are provided with notches 30 with which the downwardly projecting flange 31 of the protector plate 32 cooperates. The flange 3l serves to support the protector plate and the latter is provided with inwardly extending lugs 33 that are adapted to engage in notches 34 on the outer surface of wall 25. The protector plates are also provided with two pairs of lugs 35 that are adapted to receive the head 36 of bolts 29, and when the latter are tightened, the protector plates are securely held in place. One of the assemblies shown in Fig. 4 is placed between the inner end of the trunnion and each of the channels in the manner shown in Fig. 2. It will be observed from Fig. 1 that the inner end of the trunnion is provided with a groove 37 into which the upper end 38 of wall 22 extends. The interengagement between parts 37 and 38 serves to hold the inner ends of these assemblies and for the purpose of positively securing them in place, a wedge 40 is provided for each assembly. These wedges are held in place by hook bolts 41, one end 42 of which projects through an opening in the webb of the channel and the other end of which is provided with a nut 43. By tightening the nut the wedge can be forced inwardly and will positively anchor the assembly in place in a manner that is quite apparent from an inspection of Figs. 1 and 3. From Fig. l it will be Aseen that the tubular lining of trunnion 4 that is associated with head 3 extends inwardly a distance substantially equal to the width of walls 23 and 24, and the upper ends of the latter terminate adjacent the partitions between the compartments 17.

At this point attention is called to Figs. 4, 5 and 6 from which it will be seen that the lower ends of the protector plates 32 terminate a short distance above the upper surface of the grates so as to form openings through which the ground ore may enter. From Fig. 6 it will be observed that the lower edge of the sector-plate instead of being parallel with the upper surface of the grate, is inclined with respect to this surface and therefore if a ball should become so badly worn that it will enter the space above the grate, it will have an opportunity to escape from this position because it will roll from the narrowest part t0 the widest part of this opening, when the mill is operating.

From Fig. 1 it will be seen that in addition to the wedges 40, the assemblies shown in'Fig. 4 are held in place by means of a circular member 44, the center portion of which is conical as indicated by numeral 45. The conical portion 45 extends into a conical opening in the liner and is secured to the latter by means of a bolt 46 and nuts 47. Member 44 extends over` the inner ends of the protector plates and in addition to holding the assemblies in place, also forms a seal that prevents l ground material from passing into the spaces between the assemblies.

Let us now assume that the machine shown in the drawings and described herein is rotated by suitable means so that the attrition members will roll along the inner surfaces of the liner blocks, and that ore is introduced into the crushing chamber through the opening in liner 14. The ore particles will mix with the attrition members and the latter will grind them into a ne powder in a manner well understood. The ground material will pass beneath the ends of the protector plate and into the space above the grates, and from this space it will pass through the grates and into the reception chamber. It is evident that the ground material will not of itself travel upwardly into the opening in the discharge outlet, but when the machine rotates, the material will be carried upwardly until it reaches a place above the center of the machine and will then fall through the action of gravity and travel in the path indicated by arrows 48 and will pass outwardly through the outlet opening.

It will be apparent from Fig. 1 that the protector plates prevent the attrition members from 1 entering the space directly above the grates and therefore the grates need not be as strong as they would have to be if they were required to support the attrition members.

The mill described above and illustrated in the drawings differs from the ordinary mills of this type in several particulars, but the most important is this, that the grates instead of extending substantially transversely of the drum or of the crushing chamber extend in the direction of chords, when they are straight, or if they are curved then they may be concentric with the drum. The grates form extensions of the inner surface of the lining and the material passes through them in a radial direction as distinguished from the usual way in which the ground material passes through the grates in the direction of the length of the drum.

There are many advantages that result from this construction among the most important is this, that the pulp line can be kept very low and therefore the minimum number of attrition members can be used as well as the minimum amount of ore and this reduces the load and the power required to operate the mill. The grates and grate assemblies can be independently replaced if broken or worn. With mills of the ordinary type when used for wet grinding, the discharge of ground products is effected by the ilow of water through the grates carrying With it the particles held in suspension. The particles which are too large to be held in suspension naturally precipitate to the lowest level in the mill, from which position escape is diicult because of insulcient flow of water at this level to overcome to any great extent the action of gravity on these heavier particles.

The accumulation of these particles in the lower level of the mill tends to restrict the ow of water through the grate at this level. It follows then that the bulk of the water which is constantly being added to the mill contents leaves the mill through the grates at a level above that of the accumulation of larger particles; therefore, the heavier particles remain in spite of the fact that they are small enough to pass through the grate were they motivated in that direction.

When this mill is used for wet grinding, the iiow of water takes place at the lowest level', thereby creating a positive current through the lower strata so to speak, which works in conjunction with gravity to discharge both the particles held in suspension and those heavier ones which may have precipitated, thereby increasing the discharge capacity.

Having described the invention what I claim as new is:

1. A mill of the character described, comprising a substantially cylindrical shell provided at its ends with closure heads, each of the heads having a tubular trunnion concentric with the shell, the opening through one trunnion forming the feed and the opening through the other forming the discharge, the inside of the shell having liners which form the outer wall of a crushing compartment, suitable attrition bodies in the crushing compartment, a plurality of substantially triangular hollow grate assemblies located between one end of the lining and the discharge head, each assembly having an outer and an inner Wall, a portion of the inner wall being inclined towards the outer wall, the base being wider than the distance between the lower ends of the inner and outer walls and provided with an upper edge spaced from the lower end of the inner wall so ing the discharge, the inside of the shell, having liners which form the outer wall of a. crushing compartment and terminating a short distance from the inside of the discharge closure head. suitable attrition bodies in the crushing compartment, a plurality of substantially triangular hollow grate assemblies located between one end of the lining and the discharge head, each assembly having an inner and an outer wall the lower portion of the inner wall being inclined towards the outer wall, the base being wider than the distance between the lower ends of the inner and outer walls and provided with an upper edge spacedfrom the lower end of the inner wall so as to provide an opening, a grate located in the opening, means for securing each assembly in place and a substantially triangular protector plate secured to the inner surface of .each assembly, the base oi each plate terminating a short distance above the plane of the upper surface of the grate.

3. A grate assembly for use in mills of the character described, comprising, a substantially triangular hollow member having an outer wall, two side walls, an inner wall and a bottom, the inner wall having its lower end nearer to the outer wall than its upper end, the bottom having an upwardly extending edge spaced from the lower end of the inner wall whereby an opening is formed, and a grate located in the opening.

4. A grate assembly for use in mills of the character described, comprising a substantially triangular hollow member having an outer wall, two side walls, an inner wall and a bottom, the inner wall having its lower end nearer to the outer wall than its upper end, the bottom having an upwardly extending edge spaced from the lower end of the inner wall whereby an opening is formed, a grate located in the opening and a substantially triangular guard plate secured to the inner surface of the inner wall.

5. In a.machine of the class described having a drum comprising a cylinder with an intake and a discharge head, a plurality of grate assemblies adjacent the discharge head, the discharge head having a tubular trunnion, a portion of which extends to the inside of the head, said portion having a groove in its outer surface, each of the grate assemblies having a portion projecting into the groove and means comprising wedges and anchoring bolts for forcing the assemblies against the head and against the trunnions.

6. A mill of the character described, comprising, a substantially cylindrical shell mounted for rotation about its own axis, the mounting means comprising two hollow trunnions, one of which provides a feed opening and the other a discharge opening, the inside of the shell form-I ing `a crushing compartment, suitable attrition bodies in the crushing compartment, the inner surface of t-he shell having removable liners, terminating short of the discharge end, gra-te sections between the ends of the liners and the discharge end, the inner surfaces of the grates being substantially parallel with the axis of rotation, the outer surfaces of the grate sections being spaced from the inside of the cylindrical shell, attrition bodies in the crushing compartment. guard plates between the crushing compartment and the grates. and means effective on the rotation of the shell for conveying the material that has passed through the grates to the discharge opening.

'7. A mill of the character described, comprising a substantially cylindrical shell provided at its ends with closure heads, each of the heads having a tubular trunnion concentric with the shell, the opening through one trunnion forming the feed and the opening through the other forming the discharge, the inner surface of the shell having removable liners extending from the end closure having the feed opening and terminating a short distance from the end closure having the discharge opening, grates located in the shell between the ends of the liners and the discharge end closure, the inner surfaces of the grates being substantially parallel with the axis of rotation, the outer surfaces of the grates being spaced from the inside of the shell, guard plates between the liner surfaces and the grates, attrition bodies in the compartment whose wall is formed by the inner surfaces of the liners, and means for transferring the ground material that has passed through the grates to the discharge opening.

8. A mill of the character described, comprising a substantially cylindrical shell provided at its ends with closure heads, each of the heads having a tubular trunnion concentric with the shell, the opening through one trunnion forming the feed and the opening through the other forming the discharge, removable liners extending from the intake head to a point some distance from the inside of the discharge closure head, grates located in the space between the ends of the liners and the inside of the discharge closure head, the inner surfaces of the grates being in substantial alignment with the inside surfaces of the liners, the outer surfaces of the grates being spaced from the inside surfaces of the liners, the outer edge of the guard plate being located substantially at the juncture of the liners and the grates, attrition means in the compartment included between the intake end closure and the guard plate, and means for transferring the material that has passed through the grates to the discharge opening as transferring the material that passes through the grate to the discharge opening in the discharge head when the cylinder is rotated.

10. In a mill of the character described, the combination of a rotary cylindrical shell, a feed head and a discharge head therefor, each head having an opening, the inner surface of the shell being provided with removable liners which terminate short of the discharge head, grates located between the discharge head and the adjacent end of the liners, the grates forming extensions of the inner surface of the lining, the outside surfaces of the grates being spaced from the inside of the shell, means for holding the grates in position, means for transferring the ground material that has passed through the grates to the discharge opening, and protector plates extending radially from the center and terminating adjacent the lining surface for protecting the grates.

ll. A ball mill having a crushing chamber provided with a protective lining, a plurality of grates whose surfaces form extensions of the inner surface of the lining and which have their inner surfaces substantially parallel with the axis of rotation, a radial protector plate extending from near the center of chamber to a point adjacent the inner surface of the liners, but terminating short of this surface, and attrition members in the crushing chamber.

12. A ball mill comprising a cylindrical drum having a tubular intake head at one end and a discharge head provided with a tubular trunnion at the other, the inner surface of the drum being provided with a lining terminating short of the discharge head, grates located in the drum between the end of the lining and the discharge head, the grates forming extensions of the inner surface of the lining, and means for transferring the material that passes through the grates to the inner end of the tubular trunnion in the discharge head when the drum is rotated.

13. A ball mill, or the like, having a substantially cylindrical shell mounted for rotation aboutits axis, one end of the inner surface of the shell having removable liners and the other end a separate substantially cylindrical grate section located Within the shell and spaced from the inside thereof through which the material can pass 'in a radial direction, and means for raising the ground material to the center of the shell and discharging it as the shell rotates.

ELMER L. VAN PELT.