US3539115A - Pump and ball mill - Google Patents

Description

United States Patent Filed Verle W. Woods c/o Crop King Company, P. 0. Box 574, Yakima, Washington 98901 May 8, 1969 Continuation of Ser. No. 634,303,

Apr. 27, 1970, abandoned Patented Nov. 10, 1970 inventor Appl. No.

569,069 10/1896 Snow.... 24l/46.15 1,024,414 4/1912 Morel 241/173X 1,028,867 6/1912 Emerick 24l/173X 1,690,168 11/1928 Hopkins 241/173X 1,938,045 12/1933 Schmidt 241/107X 2,327,402 8/1943 Clark 24l/46.15 2,614,757 10/1952 OFarrell '241/90X Primary Examiner-Robert C. Riordon Assistant Examiner-Donald G. Kelly Attorney Wells and St. John ABSTRACT: Apparatus combining the functions of a centrifugal type pump and a ball mill. The apparatus is used to recirculate and grind solid particles in a fluid suspension. The particles to be reduced in size are continuously circulated by a conventional impeller within a pump casing 10. The grinding action is achieved by a series of spherical balls 20 which ride along axially spaced shoulders 18 on a ball race assembly. Apertures provide fluid circulation from the interior of the pump casing to its outlet.

Patented New. 10, 1970 3,539,115

Sheet 1 012 INVENTOR. V5816 W 14 0005 Patented .Nov. 10, W70 3,539,115

l I I j J I H 3 I4 25 m /7 /0 24 STORAGE I q TANK lZ PUMP AND 0 BALL MILL J r I INVENTOR.

VRL W 14/0005 PUMP AND BALL MILL CROSS-REFERENCE TO RELATED APPLICATION This is a continuation of application Ser. No. 634,303, filed Apr. 27, 1967, and now abandoned.

BACKGROUND OF THE INVENTION US. Pat. No. 2,957,803 discloses a method of preparing suspensions byconstant recirculation of particulated solid material and liquid carrier by means of a pump, the grinding of the insoluble solid particles being accomplished by the mechanical interaction of the particles under the forces induced by the pump action. The method is particularly adapted to the preparation of liquid suspensions of insoluble pesti cides. A further modification of the basic method is disclosed in US. Pat. No. 3,184,380. While these methods produce a commercially acceptable suspension in most instances, one practical difficulty encountered in their application is that a small percentage of particles are never reduced to the fine particle size sometimes required in pesticide applications. Furthermore, the length of time required to reduce the desired fine size of particles by the disclosed method of my two prior patents is rather long, being on the order of 48 hours.

One object of the present invention is to provide a modified pump assembly for use in the recirculating method of forming suspensions which mechanically grinds solid particles as they are being recirculated.

A most important object is to introduce a mechanical grinding step in the earlier processes without any detrimental effects due to increase of temperature as the particles are ground.

Another object of the invention is to provide a simple combination of a ball mill and circulatory pump which provides maximum ball pressure for the size of unit utilized.

Another object of the invention is to provide a combined ball mill and pump wherein the ball races are maintained in maximum operating condition regardless of wear.

These and further objects will be evident from the following disclosure of one preferred embodiment of the invention. Minor deviations are possible in the structure disclosed, and are not to be excluded by the details of this embodiment.

SUMMARY OF THE INVENTION The apparatus basically provides a unique combination of a centrifugal pump and a ball mill. The unit can be operated in any orientation, whether vertical, horizontal, or otherwise. The ball mill assembly is mounted coaxially about the impeller of a centrifugal pump, so that all fluid being handled through the pump must pass through the ball raceway. In this manner, solid particles are ground by the action of the balls along the raceway, and a more efficient size reduction is obtained than is possible by prior recirculation processes. I

The apparatus is preferably coupled to a recirculating type structure wherein the fluid and solid particles are normally maintained in a relatively large storage tank. By utilizing the particular grinding apparatus shown in conjunction with a cooled storage tank, particles can be effectively ground without substantially raising their temperatures. This is particularly important in the grinding of pesticide chemicals which often are particularly sensitive to heat increases. Since the grinding action is momentary and since the much greater volume of fluid is being continuously circulated to and from a storage system wherein small increases in temperature can be quickly dissipated through the large fluid body, I have found that I can successfully grind solid particles which cannot be mechanically ground by conventional ball mill procedures.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an end elevation view of a typical pump and ball mill assembly with the inlet face plate removed;

FIG. 2 is a sectional elevation view taken along line 2-2 in FIG. 1 showing the inlet face plate in place;

FIG. 3 is a perspective view of the ball race;

FIG. 4 is an enlarged fragmentary view of the ball race area;

FIG. S'is an enlarged view illustrating the wearing action of the balls and raceway during the life of the apparatus, and

FIG. 6 is a schematic flow diagram illustrating the use of the pump and ball mill in a recirculation system.

DESCRIPTION OF THE PREFERRED EMBODIMENT The apparatus shown in the drawings is designed particularly for use in conjunction with' the method and illustrative structure as set out in US. Pat. No. 2,957,803.

In utilizing' such a combination for the preparation of suspensions of pesticides, without any mechanical grinding, the reduction in size of the solid particles is accomplished by erosion and collision of particles. I'have found that at least a small percentage of the larger solid particles are never broken by this random action and therefore one cannot guarantee that every particle in a suspension will pass through a relatively fine screen. In addition, grinding by pumping action along requires considerable time, which can be effectively reduced by utilization of the present apparatus.

As seen in the drawings, a conventional centrifugal pump casing 10 is used as the basic pump structure. Casing 10 includes an annular wall section 11 terminating at a tangential outlet 12. Casing 10 also includes an inlet fact plate 14 secured by bolts 24 and including an axial inlet opening 16. A central impeller 13 is mountedon an impeller shaft 15 suitably powered by a conventional motor (not shown).

As in the usual pump assembly, liquid is received axially into the pump casing through the inlet opening 16, is forced radially outward by the action of the impeller 13 and exits through outlet 12. In forming a suspension by the methods described in my prior patents, the volume of the storage tank is very large in comparison with the volume of the pump and supply lines to and from the pump, so that the great percentage of liquid and solid particles are being agitated in the large tank volume at any given time. This is necessary when reducing the size of particles that are extremely sensitive to heat. The temperature in the large tank can be closely controlled, using exterior cooling if required. A small rise in temperature in a small volume of the fluid and suspended material will be promptly dissipated when it is returned to the large tank area.

To add mechanical grinding to the system, there is added a ball race assembly designated generally by the numeral 16. This includes an annular cylinder wall 17 positioned coaxially about the impeller 13 at a position radially outward therefrom. The wall 17 rests against the inner shoulder formed about the annular wall 11. The cylindrical wall 17 is held in place within the assembled casing 10 by abutment with the inner surface of the inlet face plate 14.

Projecting inwardly from the cylindrical wall 17 are two axially spaced shoulders 18. The wall 17 and shoulders 18 are preferably fabricated of normal steel by welding the shoulders 18 to the wall 17. The shoulders 18 are preferably not hardened steel, as will be explained below. Each shoulder 18 has an inner inclined angular edge 19 on which the moving balls 20 of the mill roll.

The balls 20 extend about the shoulders 18 and are located between them and a disc 21 mounted on shaft 15 adjacent to the impeller 13. The peripheral edge of disc 21 is tapered so as to extend slightly past the minimum ball radius relative to the axis of shaft 15; In this way, disc 21 always overlaps the balls when the unit is stationary and prevents them from falling inwardly within casing 10. The balls are prevented from falling outwardly by a shoulder 23 extending axially inward on the plate 14.

To prevent any area of quiet fluid from forming back of the smooth disc 21, some type of agitating device should be formed on the disc 21. As illustrated, there is a circular saw blade 22 mounted at the back of disc 21. The tooth configuration of the blade 22 maintains the fluid at the inner portion of casing 10 in motion and prevents the accumulation of particles in this area. Any toothed formation on or adjacent to disc 21 will accomplish this effect.

The cylindrical wall 17 is apertured about its periphery as can be best seen in FlG. 3. The apertures 25 are positioned intermediate the shoulders 18, so as to provide maximum fluid communication between the area adjacent impeller 13 and the interior of pump wall 11.

One advantage of the structure shown is that it can be used in any position, whether horizontal, vertical or otherwise. The balls are restricted so that they always remain in position to roll about the inclined faces 19 of the respective shoulders 18. When the unit is at rest, the balls 20 are prevented from falling out of position by the disc 21 and shoulder 23. As shown in FIG. 4, the extension of disc 21 is such that the minimum separation possible between disc 21 and the adjacent shoulder 18 is less than the minimum ball diameter. As the balls 20 wear into theshoulders 18, they will form a deepening channel. However, the maximum width of the shoulder is limited by the maximum diameter of balls 20. The no wear pointA on the shoulder 18 adjacent to disc 21 is separated from the maximum extension of disc 21 by less than the minimum ball diameter. Similarly, the shoulder 23 on plate 14 is separated from the no wear point B on the adjacent shoulder 18 and from the disc 21 by a distance less than the minimum ball diameter. Thus, the balls 20 are always maintained in positions at which they can be forced outwardly to roll about the shoulders 18 under the influence of fluid properly propelled by the impeller 13.

To maintain maximum grinding efficiency, it is necessary to insure that the balls 20 roll about the shoulders 18 with line contact against the shoulder surfaces along planes that are offset from the plane containing the ball centers. The faces 19 are initially flat to provide such line contact. As the hardened steel of the balls 20 gradually wears into the shoulders 18 of softer material, the balls 20 will form annular grooves complementary to their curvatures. By providing balls 20 of differing diameters this wearing action is utilized to insure the desired line contact. The balls 20 are arranged in two or more groups, balanced diametrically across the mechanism. As the balls 20 of different diameter each form grooves in the shoulders 18, a series of annular ridges will be formed as shown by C in FIG. 5. This action is exaggerated in FIG. 5, but is illustrative of the actual operation, which enhances the grinding efficiency of the rolling balls.

in operation, the rotation of impeller 13 imparts rolling movement to the balls 20 through the action of the fluid circulating into and from the pump. Solid particles in this fluid must pass about the balls 20 and through apertures 25 as they exit from the pump along with the carrier fluid. The larger particles carried by the fluid will be mechanically ground by the rolling action of the balls 20 along the shoulders 18. The larger sizes are ground first since the finer particles can pass more freely from the assembly. By utilizing the combined mechanical grinding along with the fluid particle reducing operation previously disclosed in US. Pat. No. 2,957,803, reduction of substantially all particles to a given screen size can be guaranteed. The apparatus is capable of continuous long life use, since the balls 20 form deepening race surfaces within shoulders 18, with no deterioration of the grinding operation. When the shoulders 18 have been subjected to maximum wear, only the wall 17 and attached shoulders 18 need be replaced. The balls 20 may be replaced when necessary. Slight wearing of balls 20 and the normal wear to which the shoulders 18 are subjected does not distract from the operation of the unit.

In addition to the pump and ball mill assembly shown herein, the complete apparatus would include a relatively large volume storage tank or surge tank in which the liquid suspension is continuously cooled and agitated, the fluid being drawn from the tank source, passed through the pump and ball mill, and returned to the tank as illustrated in schematic FIG. 6.

l have found that by utilizing the unit in conjunction with a large agitated storage tank, heat sensitive solid material suspended in a liquid can be effectively ground to fine particle sizes without damaging the particles. This is due to the momentary grinding action as the particles pass through the I crements of onesixteenth of an inch have been successfully used, although the difference between adjacent ball sizes can be more or less than that amount.

The apparatus shown can be readily equipped to use multiple races in a single pump by widening the pump and impeller areas. Furthermore, progressive grinding and pumping units can be connected in series if more rapid grinding is desired and if the material being ground can accommodate the increased heat conditions.

The design of the impeller 13 will, of course, be dictated by the horse power of the motor operating the unit, the viscosity of the suspension, the fluid lift in the system and other common factors. Any desired shape of impeller can be substituted for the typical element illustrated.

Various modifications can be made in the illustrated structure, depending upon the size and volume requirements of the unit. For this reason only the following claims are intended to set out the scope of my invention.

lclaim:

l. A pump and ball mill, comprising:

a stationary member;

fluid impeller means rotatably mounted on said member about a first axis for imparting to fluid material directed thereto both a circular and radial component of movement outward from the impeller means;

ball race means fixed to the stationary member, said ball race means including an inwardly facing circular surface centered about said first axis and spaced radially outward from the impeller means, said ball race means having radial openings formed therethrough at said surface;

ball means located between said impeller means and said ball race means for rolling contact against the circular surface thereof along at least two lines respectively positioned at opposite axial sides of the radial openings in response to movement imparted to fluid material by said impeller means;

means for directing fluid material to the impeller means;

and means for receiving fluid material passed outwardly through the radial openings of said ball race means.

2. An apparatus as set out in claim 1 wherein said ball race means comprises:

a cylindrical wall;

a pair of axially spaced shoulders projecting inwardly from the wall and defining said surface; and

said openings being provided by a plurality of apertures formed through said wall intermediate said shoulders.

3. An apparatus as set out in claim 1 wherein there is line contact between said ball means and said ball race means along planes displaced from the ball centers.

4. An apparatus as set out in claim 1 wherein there is line contact between said ball means and said ball race means along planes displaced from the ball centers; said ball means including at least two paired groups of balls positioned in a diametrically balanced relationship, each group of balls being of a diameter different than the other.

5. An apparatus as set out in claim 1 wherein the minimum separation between said ball race means and said impeller means is less than the minimum spherical diameter of said ball means.

6. In a pump apparatus of the type comprising an annular casing having an axial fluid inlet and a tangential fluid outlet positioned radially outward of said inlet, the improvement comprising: 7

a central impeller assembly rotatably mounted by said casing about the axis of the fluid inlet for imparting to fluid material directed thereto through said fluid inlet both a circular and a radial component of movement outward from the impeller assembly;

ball race means fixed to the casing, said ball race means including an inwardly facing circular surface centered about said axis and spaced radially outward from the impeller assembly, said ball race means having radial openings formed therethrough at said surface; and

a plurality of spherical balls located intermediate said impeller assembly and said ball race means for rolling contact of each ball against the circular surface thereof along at least two lines respectively positioned at opposite axial sides of the radial openings in response to movement imparted to fluid material by said impeller assembly.

7. An apparatus as set out in claim 6 wherein said ball race means comprises:

a cylindrical wall;

a pair of axially spaced shoulders projecting inwardly from the wall and defining said surface; and

said openings being provided by a plurality of apertures formed through said wall intermediate said shoulders.

8. In combination with a source of liquid having solid particles suspended therein and a pump assembly for removing material from the source and returning said material to the source in a recirculating system, the improvement comprising:

a stationary pump casing;

a fluid impeller rotatably mounted on said casing about a first axis for imparting to fluid material directed thereto both a circular and a radial component of movement outward from the impeller;

ball race means affixed to the casing, said ball race means including an inwardly facing circular surface centered about said axis and spaced radially outward from the impeller, said ball race means having radial openings formed therethrough at said surface;

a circular row of balls located between said impeller and said ball race means for rolling contact of each ball against the circular surface along at least two lines respectively positioned at opposite axial sides of the radial openings in response to movement imparted to fluid and solid material suspended therein by said impeller;

means for directing fluid and solid material suspended therein from said source to the impeller; and

means for returning to I said source the fluid and solid material suspended therein passed outwardly through the radial openings of said ball race means.

' 9. An apparatus as set out in claim 8 wherein said ball race means comprises:

a cylindrical wall;

a pair of axially spaced shoulders projecting inwardly from the wall and defining said surface; and said openings being provided by a plurality of apertures formed through said wall intermediate said shoulders.

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