US2999649A - Apparatus for continuously crushing and selectively discharging solid materials - Google Patents

Description

P 1961 c. s. RADCLIFFE 2,999,649

APPARATUS FOR CONTINUOUSLY CRUSHING AND SELECTIVELY DISCHARGING SOLID MATERIALS Filed March 1, 1956 2 Sheets-Sheet 1 5C;- IZ. 26 57 gill/d f Sept. 12, 1961 C. S. RADCLIFFE APPARATU CONTINUOUSLY CRUSHIN SELECTIVELY DISCHARGING SOLID MATE G AN RIALS 2 SheetsSheet 2 S FOR Filed March 1. 1956 United States Patent 2,539,649 APPTUS FUR CONTINUOUSLY CRUSHING AND SELECTIVELY DISCHARGING SOLE MA- TS Charles S. Radcliffe, Philadelphia, Pa., assignor to Concentro Corporation, Philadelphia, Pa., a corporation of Pennsylvania Filed Mar. 1, 1956, Ser. No. 568,727 11 (llaims. (Cl. 241-39) This invention relates to the crushing or grinding of solid materials in a liquid medium. It was conceived and developed as an improvement for crushing ores in the presence of water to reduce them to a desired degree of fineness, and for removing the resulting suspension continuously from the zone of the crushing operation.

As an example of material which presents an ideal example of the problems of the prior art and the advantages attained in the practice of the invention, it Will be helpful for us to consider the grinding of mica, as this illustration will be useful not only in relation to treatment of this particular material but also of other materials presenting simi ar problems or opportunities.

In the typical wet grinding of so-called scrap mica, the mica ore, which may previously have been subjected to crushing action to break up excessively large plates or lumps, and washed to rid it of easily removable impurities, is ground in a so-called chaser mill. In this mill the product is subjected to crushing and grinding action by large wooden rollers acting against the mica mass while upon a wooden flooring. During the course of the grinding, which ordinarily requires about eight hours, water is added from time to time as required to avoid excessive friction. Both the slowness of the grinding and the addi tion of the necessary amount of water from time to time are necessary aspects of the process, for otherwise the heat generated and retained within the mass will act destructively to burn the mica and abrade the edges, thereby destroying the desirable sheen and luster of the ground, product. In use in the paint industry in particular, the value of the mica would be impaired or destroyed in regard to mixing and reflection of light, if these precautions were not taken. After the grinding process is completed, the mica is subjected to treatment in sand vats, settling tanks, slip tanks for steam treatment, and filter pressed, after which it is dried and screened. The grinding and other operations preceding the final drying operation frequently require as much as six days for completion in the treatment of the product.

When an efiort is made to susbtitute for this slow and laborious process a rapid and continuous one, a number of problems and difiiculties are encountered. In the first place, it is difiicult to conduct such a process in a manner providing crushing of the ore to the desired degree of fineness with desired rapidity and if this is done, there is grave danger of damaging parts of the mica mass. The mass passed to the crushing or grinding operation ordinarily includes some particles which are much smaller than others, and there is particular danger of injuring these smaller particles if the process is performed in such a way as to continue to subject them to the grinding and crushing forces until substantially all of the larger particles are reduced to the desired degree of fineness. Efforts to apply continuous or rapid methods to the grinding of mica and other materials presenting similar problems have accordingly been thwarted, in the first place by the fact that considerable energy and additional time were required to grind the remaining portion of the mass, after a substantial part had already been ground to the desired degree of fineness, and in the second place by the fact that this additional expenditure of energy and time was not only wasteful, but was actually destructive of the quality of particles already ground to this desired degree of fineness.

A primary object of the invention has accordingly been to provide an apparatus for crushing and grinding of solid materials, in which both the feed and discharge of liquid and solids is performed continuously, without encountering any of the difliculties discussed above.

A further object has been to provide improvements which results in removal promptly from the field of action of the crushing operation, of particles which have already been crushed to the desired degree, While retaining in or returning to the zone where the crushing operation is being performed, particles which have not yet been re duced to this extent. A considerable economy is thus effected by avoidance of performing unnecessary work on particles already ground adequately, while an actual improvement in quality is attained by the removal of these particles from the field of action where they might sustain damage from continued crushing treatment.

A further object has been to provide apparatus to effectively classify, by employment of two separate centrifugal bowls, in series and with selective recirculation to attain the desired results. A further object has been to employ in such an operation two separate centrifugal rotors, one within the other, which cooperate both in the classification to produce an aqueous efiiuent containing ground or crushed material of substantially uniform particle size, and in the preceding crushing operation by which the particles are reduced to this desired size.

A further object has been to provide adjustments of the elements employed in the crushing step and in con' trol of the discharge efiluent, so that the operator may con-- trol in a desired manner the crushing operation by which, the particles are classified under the influence of centrife ugal force.

Still further objects and advantages and the manner in; which they have been attained will be evident from read.:

ing of the following detailed description in the lightlof the outer annular parts of said apparatus, FIGURES 3 and 4 are cross-sections on the lines 3-3" and 44 of FIGURE 1, respectively,

FIGURE 5 is an elevational view looking in the same. general direction as FIGURE 1, but illustrating associated ap'pa'ratus'parts in their relationship to the parts forming the primary features of this invention, FIGURE 6 is a view in elevation of the apparatus illus-''- trated in FIGURE 5, as seen from the right end of said uniform and fine particle size is ordinarily subjected to preliminary mechanical disintegration, as by a hammer mill or gear grinding process, so that none of the materialis of very large size, e.g. in excess of 3" diameter. The steps preliminary to this invention may also include screening and shaker table treatments, or other treatmentsknown in the art for preliminary treatment of the crude:

ore or the like, to insure that the solid material treated. by the present invention is of reasonably uniform charac-: ter and adapted to this further treatment.

In the practice of the process of this invention, the solid;

materials, which have preferably been subjected to preliminary treatments as discussed above, are subjected to, crushing force in the presence of liquid to produce a suspension of the crushed or ground particles in the liquid, and this suspension is then subjected to centrifugal sedimentation to separate from the remaining suspension solids which have not been reduced to the desired degree of fineness, while the remaining liquid suspension is discharged continuously, and the oversize particles separated by the sedimentation are returned continuously to the primary crushing or grinding step, for further treatment together with a fresh quantity of liquid and solids. By repetition of this'cycle indefinitely in a continuous process, adequately ground particles are removed promptly from the zone of application of the crushing force, while the remainder are recycled and/or retained in that zone only long or often enough to attain the desired result, and the resulting'finer particles are then promptly removed. The suspensionof these finer particles in liquid may then be subjected to sedimentation, drying and other steps known to the art to provide the finished product.

' This invention provides an unusually effective means of achieving the desired rapid crushing with selective sedimentation by employing centrifugal force in both the crushing and ensuing centrifugal sedimentation steps, with theme of the two rotors to effect the crushing by kneading'of the wet mass of solids within the bowl space between the inner wall of an outer centrifugal rotor and the outer wall of an inner eccentrically mounted centrifugal rotor. By producing or permitting relative rotation between the rotors, there is thus obtained the desired kneading action, as different portions of the outer circumference of the inner rotor come progressively into closest, or kneading, proximity to the outer rotor. A part of the liquid fed continuously to the outer rotor spills over through holes through an inner radial part of a lateral wall into the inner rotor, and this liquid carries with it finer solids, While coarser solids remain in the first rotor for continued kneading along with further solids and liquidbeing fed to this rotor continuously. The suspension spilling over'into the'bowl space of the second rotor is subjected to further centrifugal sedimentation, and larger solids arereturned through holes at the outer part ofthe bowl space to the first rotor.

It will be seen that the process and apparatus provide features including steps of centrifugal sedimentation conducted in series and cyclically, but that the throughput is continuous and that each particle is subjected only to such continued, or repeated, kneading as may be necessary to reduce it as desired. By these features, economy and uniformity are attained, while the features of kneading and selective removal provide moderate and not too prolonged application of force, thereby preventing the damage which has heretofore been sustained when such materials as mica, for example, have been subjected to too violent, or too prolonged, grinding.

LAS illustrated particularly-in FIGURES 1 and 5 of the drawing, the apparatus provides means such as a hopper 10.and chute 12, and a conduit 11, by which the solid material, such as an ore, and liquid, such as water, may be fed under suitable control, continuously or intermittently, at 'a desired rate to the crushing and sedimenting elements. As illustrated particularly in FIGURES 1 and 2, these elements include an outer ccntrifugalrotor 13 positively driven by shaft .14, and an inner centrifugal rotor 15 which is mounted upon shaft 16 for differential rotation with respect to rotor 13, preferably by being positively driven at a different speed. By reference to FIGURES 1 and5, it will be seen that the shafts 14 and 16 are disaligned, and that rotors '13 and 15 are hence mounted for eccentric rotation relative to each other. Driving power may be applied to both of these shafts simultaneously from motor 17 through separate belt andpulley drives 18 and19. While the speeds of these rotors may vary within wide limits, in a typical treatment of a mica ore satisfactory performance has been attained by rotation of an outer rotor having an inside diameter of inches, at a speed of 1725 r.p.m. while rotating the inner rotor which has an outer diameter of 8 /2 inches, at a speed of 2146 r.p.m.

In the continuous practice of the process, water may be fed continuously during such rotation into a space defined between a frusto-conical sleeve or baflle 22 secured to a radial wall 23 of rotor 15 and the inner side of said wall, and discharged through holes 24 into the bowl space 25 of that rotor. The inner rotor 15 has a plurality of holes 26 in its side wall 23, and these holes are located in the side wall on a circumference which is within the line of skimming established by the radial location of a stationary skimming nozzle 27. However, since the-two rotors are eccentrically mounted, the holes 26 will be closer to the outer circumference 28 of the bowl space of rotor 13 at some points than others, with the consequence that some of these holes 26 will have their outer edges beneath the inner circumference of the liquid annulus maintained in rotor 13'while other holes 26 will be above (inside) this liquid annulus line 29, as illustrated in the upper and lower parts of FIGURE 1. A pulsating pumping action to impel water from rotor 13 into rotor 15 is therefore produced upon continued feed of water to rotor 13, as water is discharged continuously from the established level in the bowl space 32 of rotor 15 by skimming nozzle 27 and into skimming tube 33.

After water has been fed into the apparatus to fill the two rotors to the lines indicated at 29 and 34, respectively, andwater has begun to discharge from skimming nozzle 27 and tube 33, feed of solids is commenced through chute 12. The solids, being heavier than the water,are thrown to the outer circumference of the rotor 13, and are impelled, by a pulsating action, across the space between the outer circumference of rotor 15 and the inner circumferential wall of rotor 13, thereby providing a -kneading action upon these solids, as they accumulate in the bowl space within the inner circumferential'wall of rotor 13. Solids of relatively large size will stay in this bowl space until a sufiicient quantity of solids has accumulated to provide the desired resistance to produce the kneading action by progressive approach of different portions of the outer wall of rotor 15 to the solids in this bowl space. Just as soon as a part of the solids have beencrushed to a degree of fineness suificient to cause them to flow with the liquid, in its pulsating motion through holes '26, theywill be discharged through these holes and around the outer end of annular baflie 35 to themain body of the bowl space of rotor 15. These solids will thus be subjected to still further centrifugal sedimenting treatment within the rotor 15, and the smaller particles will tend to flow to the inner circumference of the liquid at 34 within this bowl space, along with the general'flow of liquid from this rotor. At the same time, the solids of somewhat larger size which have been passed to this inner rotor 15 through holes 26 and around the baffie or dam 35, will be discharged through holes 36 in the outer portion of rotor 15, and returned thus to the kneading zone between rotors 13 and 15. The holes 36 are preferably :formed inthe lateral wall 37 of the rotor opposite towall 23, at a point adjacent the inner circumference of the bowl space.

The feed of, liquid to the rotor is continued duringthis continuous feedof solids, and in the case of the crushing or grinding of scrap mica, for example, it may continue in ,the'ratio of one pound ofvmica to one gallon of water fed into .the system of rotors.

The principles of the invention are best illustrated in FIGURE 20f the drawing, in which the arrows indicate direction of flow of the mica particles through the parts of the apparatus including the kneading zone between rotors 13 and 15, the holes 26 by which the particles are passed into the rotor 15, around baffle 35 and to the'bowl space of rotor 15, and the holes 36 by which the particles not yetadequately crushed are continuously recycled to the kneading zone. It will be seen that all of the solids entering rotor 15 through holes 26 are compelled to pass around the outer circumference of baflle'35. As a consequence of this, the larger solids are brought immediately into radial proximity to discharge holes 36, and only the finer ones pass inwardly and out of the rotor through skimming nozzle 27, which has its inlet or skimming edge facing in an opposite direction to the rotation of the rotor 15 containing the rotating body of liquid and solids being subjected to centrifugal classification.

Skimming discharge tube 33 is mounted for rotation on an axis which is eccentric to the axis of rotor 15 and its shaft 16, and may accordingly be adjusted in angular position to change the radial position of nozzle 27 relative to the bowl space within rotor 15. By making such adjustment, which may be accomplished by rotation of hand wheel 40 which operates through worm 38 and worm wheel quadrant 39 rotatively secured to tube 33, the apparatus will discharge finer solids if the adjustment is in a direction away from the circumference of rotor 15 and vice versa. The liquid and solids are discharged from skimming tube 33 through slurry discharge conduit 42.

The degree of eccentricity of rotor 15 relative to rotor 13 may also be adjusted to control the crushing or kneading force by varying the kneading gap or space by rotation of crank 43, which operates through worm 44, worm wheel 45 and cam 46 mounted on shaft 47, and Sliding block 48 carrying shaft 16, to change the vertical adjustment thereof.

While the invention has been described only with respect to a single specific embodiment, persons skilled in the art will be aware that it may be modified or refined in various ways while still employing its fundamental features. I therefore wish it to be understood that this invention is not to be limited in interpretation except by the scope of the following claims.

1. In an apparatus for crushing solid materials, the combination comprising a first centrifugal rotor having a circumferential wall forming the outer wall of a bowl space, means to feed liquid and solids continuously to said bowl space, a second centrifugal rotor eccentrically mounted within the first and having a bowl space with an outer circumferential wall located at least partially within said bowl space of the first in kneading proximity to said first circumferential wall, said bowl space of said second rotor communicating with an inner portion of said bowl space of said first rotor to receive a mixture of liquid and solids crushed between the circumferential walls of said rotors and discharged from said first bowl space into said second bowl space, and means for discharging continuously from an inner portion of said second rotor an efiluent comprising said liquid containing solids crushed between said circumferential walls.

2. In an apparatus for crushing solid materials, the combination comprising a first centrifugal rotor having a circumferential wall forming the outer wall of a bowl space, means to feed liquid and solids continuously to said bowl space, a second centrifugal rotor eccentrical-ly mounted within the first and having a bowl space with an outer circumferential wall located at least partially within said bowl space of the first in kneading proximity to said first circumferential wall, said bowl space of said second rotor communicating with an inner portion of said bowl space of said first rotor to receive a mixture of liquid and solids crushed between the circumferential walls of said rotors and discharged from said first bowl space into said second bowl space, means for discharging continuously from an inner portion of said second rotor an efiluent comprising said liquid containing solids crushed to a predetermined degree of fineness between said circumferential walls, and means for returning to said first rotor from said second rotor solids which have not been crushed to said predetermined degree of fineness.

3. An apparatus as defined in claim 2, in which said second rotor includes an annular, radially extending, bafiie plate having its outercircumference within an outer-por tion of the bowl space of said second rotor, said baflle plate being located in the line of flow to direct material around its outer circumference in passing to the main body of the bowl space of said second rotor.

4. An apparatus as defined in claim 3, in which a plurality of holes are provided in an outer portion of a lateral wall of said second rotor in position to receive solids and liquid from said first rotor and direct the same to the inlet side of said baffle, and a further plurality of holes are provided in an outer portion of said second rotor to return to said first rotor said solids which have not been crushed to said predetermined degree of fineness.

5. An apparatus as defined in claim 2, in which the means for discharging from said second rotor liquid containing said solids crushed to said predetermined degree of fineness is mounted for radial adjustment relatively to the circumferential wall of said second rotor to thereby control the degree of fineness of the solids so discharged therefrom.

6. An apparatus as defined in claim 2, in which the means for discharging said liquid containing solids from said second rotor is a skimming nozzle mounted in stationary position with its inlet end facing the direction of rotation of material within said second rotor.

7. In an apparatus for crushing solid materials, the combination comprising a centrifugal rotor having a circumferential wall forming the outer wall of a bowl space, a centrifugal rotor kneading member mounted within said rotor having a bowl space and mounted in a location such that at least a part of its periphery extends into close proximity to the interior side of said circumferential wall, means for feeding liquid and solids to said bowl space in said rotor and into the kneading space between the interior side of said circumferential wall and said kneading member, means for imparting rotation to said centrifugal rotor and said kneading member respectively to thereby crush solids by relative rotation between said wall and kneading member, means for discharging continuously from an inner portion of said kneading mem-, ber bowl space liquid containing solids crushed to a predetermined degree of fineness, and means for continuously returning to said kneading space from an inner portion of said kneading member rotor solids which have not been crushed to the desired degree of fineness.

8. An apparatus as defined in claim 7, in which said kneading member is an annular member eccentrically mounted with respect to said rotor with its outer circumferen'ce within the circumferential wall of said rotor.

9. An apparatus as defined in claim 8, in which said kneading member is provided with holes extending through a lateral face thereof to receive liquid containing kneaded solids, and further holes in an opposed lateral face thereof communicating at their discharge sides with said kneading space to return oversize solids thereto.

10. An apparatus as defined in claim 8, in which the drive means interconnected to said kneading member rotate the same positively at a rate different from the rate of rotation of said centrifugal rotor.

11. In an apparatus for crushing solid materials, the combination comprising a centrifugal rotor having a circumferential wall forming the outer wall of a bowl space, a hollow kneading member mounted within said rotor and mounted in a location such that at least a part of its periphery extends into close proximity to the interior side of said circumferential wall, means for feeding liquid and solids to said bowl space and into the kneading space between the interior side of said circumferential wall and said kneading member, means for imparting rotation to said centrifugal rotor and said kneading member respectively to thereby crush solids by relative rotation between said wall and said kneading member, solids fineness classifying means adjustably mounted within the kneading member and operable for selective discharge of solids of ene-e45 References Cited in the file of this patenp UNITED STATES PATENTS 1 Fields Apr. 9, 1 867 8 2 1 Keet -2 Oct. 15, Harding's A-u'g.- 7, Matts'on Feb, 21, Lyons et a1. Aug. 29, Ayers May 22, Ahlmann Apr. 29, Venable "2 Mar. 16, Kihlstedt ..2 Apr. 20,

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