US2974793A - Rotary sizing mechanism - Google Patents

Description

March 14, 1961 R. s. KUNTZ ROTARY SIZING MECHANISM 2. Sheets-Sheet 1 Filed Aug. 29, 195" INVENTOR.

RwmTa/wA/Tz ATTOQNEYJ- March 14, 1961 Filed Aug. 29, 1957 R. s. KUNTZ 2,974,793

ROTARY SIZING MECHANISM 2 Sheets-Sheet 2 VII INVENTOR. ROBERT .5. AU VTZ Mqiwaz 2,974,793 Patented Mar. 14, 1961 ROTARY SIZING MECHANISM Robert S. Kuntz, Nashwauk, Minn., assignor .to The M. A. Hanna Company, Cleveland, Ohio, a corporation of Ohio Filed Aug. 29, 1957, Ser. No. 680,964

13 Claims. (Cl. 209-106) The present invention relates to a rotary sizing mechanism and, more particularly, to a sizing or separating device wherein separation between the coarser and finer particles is effected by difierences in momentum imparted to the particles.

The principal processes of dry sizing concern separation of relatively fine particles from relatively coarse particles by imparting a motion to a mixture of the particles, so that the force of gravity can be used to discharge the finer particles through openings in a barrier which retains the relatively coarse particles and discharges them separately. In present commercial use vibrating screens, trommels, roll screens, grizzlies, are used, to mention only a few. The problems encountered in sizing are varied and as numerous as the materials being processed in industry today.

The present invention is primarily concerned with sizing mixed particles of varying shapes and mass such as crude ore and especially crude iron ore having a high moisture content. To accomplish this economically, screen capacity is of prime consideration because enormous tonnages are involved. Although vibrating screens with their attendant disadvantages are used in the sizing industry today, such screens are unsatisfactory with damp ores or if fine size separations are required unless excessive screen deck area is employed.

Prior sizing devices may be generally classified under the following two groups.

(1) Vibrating screens.-Vibrating screens use a screen deck made of wire mesh or punched plate which is attached to and supported by a steel frame. vibrated or given an oscillating or circular motion in a conventional manner by an eccentric shaft and/or a counterweight at relatively high speed. The housing containing the eccentric motion may be attached to the frame holding the screening medium. The undersize material falls through the openings in'the screen deck by gravity flow. The oversize material moves across the screen deck, which may be level or sloped, by motion vof the screen mechanism. One limitation of this type of screen is blinding of the openings wherein the screen openings become plugged with sticky material. This usually may be overcome if a wire cloth is heated or beaten manually. Such methods, however, are costly and require excessive maintenance.

(2) Roll screens.-Roll screens or grizzlies are constructed with rolls spaced at the desired distance apart, mounted in anti-friction bearings, and rotated in the same direction. This machine depends on free gravity flow of the undersize particles through measured spaces between the rolls to elfect a separation. The oversize particles are moved from the screening surface by friction between the rolls and the oversize particles. This machine is limited, however, in that there is not enough agitation of the mass being screened, and in order to maintain effective frictional contact between the roll and the oversize material, the speed of the rolls is slow. This The deck is machine also loses its effectiveness when the rolls accumulate sticky material. In one modification, an eccentricity has been added to the rolls while still maintaining a measured opening between each roll. This machine is an improvement because it agitates the mass to be screened and moves the oversize by the combing action of the eccentric shape of the roll. The speed of this machine, however, is still slow. This machine is not effective in separating sticky material without the addition of numerous bars, finger gates, and the like, for purposes of retarding the flow of the oversize particles, using the depth of bed of the oversize particles to squeeze the undersize particles through the roll openings. With dry ore the undersize is separated by free gravity flow. The oversize is moved by pushing, lifting, combing, and frictional contact of the eccentric rolls, rotating in the same direction.

To summarize, then:

(1) All machines now available are subject to blinding with sticky material. In order to remedy this fault, expensive and cumbersome methods have been employed resulting in lessened capacity and higher maintenance costs.

(2) All machines cause free gravity flow of undersize to effect separation.

(3) Mechanical screening processes ordinarily include such actions as vibrating, circular, or oscillating movements, or friction, combing, lifting, and pushing actions, sometimes aided by positioning the screening plane at a slope or angles in line with the direction of flow.

(4) Roll type machines are operated at slow speeds and vibrating and shaker screens operate at relatively high speeds.

The rotary sizer of the present invention differs from the foregoing and affords a novel technique of sizing or separating mixed particles of varying size that is vibrationless and requires a minimum of equipment and financial investment. In general, the present rotary sizer operates on differential velocities resulting from unequal sizes of the mixed particles. The size differentials may be provided directly to a natural and crude ore as it is mined from the earth. Velocity and direction are also imparted by my rotary sizer to effect the desired separation.

It is, therefore, a principal object of the present invention to provide an improved method and apparatus for sizing particles.

Another object is to provide a rotary sizing device which impacts mixed particles such that a separation may be effected by the resulting momentum of the particles.

A further object is to provide a rotor member having resilient impact vanes projecting angularly therefrom and adapted to impart momentum to mixed particles of varying sizes at various rates.

Other objects will become apparent as the description proceeds.

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims, the annexed drawings and the following description setting forth in detail certain means and one mode of carrying out the invention, such disclosed means and mode illustrating, however, but one of various ways in which the principle of the invention may be used.

In said annexed drawings:

Figures 1 and 2 are plan and side views, respectively, of a sizing mechanism embodying the present invention.

Figure 3 is a right-hand end view of Figure 2.

Figure 4 is a section of Figure l on the line 4-4.

l 2,974,793 r e vanes are secured to a bar of the rotor, and

Figure 6 is a side view of the bar of the rotor illustrating the points at which vanes may be attached.

Structure Referring to the drawings, the embodiment disclosed includes a support stand or bed for the sizing operation generally indicated at 10. The bed comprises corner posts 11 which carry opposed side beams 12 and 13 and opposed end beams 14 and 15. An end liner 16 cooperates with the end beam 15. Side liners 17 and 18 are generally coplanar with the side beams 12 and 13, respectively, and rise above the end beam 14. However, the side beams are at about the same level as the end beam 15. This arrangement permits the entry of feed stock, such as moist iron ore, over the end beam 14, and onto a feed plate 19 defining a feed box, while the exiting ore leaves the sizing bed beneath the end beam 15 and at substantially the same level as the sizing bed.

Disposed between the two ends of the bed 10 are a plurality of substantially parallel rotor members 20 which define a path of travel for the particles transverse'ly of their longitudinal axes. Each rotor comprises a bar 21 of polygonal cross section, here shown to be square, and preferably solid for purposes of strength and wear. Each bar 21 terminates at its ends in rounded portions 22 (Figure 6) for rotatively mounting the bar 21 in the sides of the sizing bed 10. Anti-friction bearings 23 journal the end portions 22 of the bar and are secured to side plates 24. The plates 24 in turn are detachably secured to the side beams 12 and 13. A sprocket 25 is also fixed to the adjacent round ends 22 of each bar 21 to rotate the bars by a link chain 26 which is trained about the sprockets 25 and over an idler sprocket 27. A motor 28 and sprocket 29 conventionally drive the link chain 26.

Referring especially to Figures and 6, the square bar 2 1 has drilled and tapped openings 30 on each face which encircle the bar 21 in a transverse direction. Several such rings of openings are spaced axially of the bar as shown in Figure 6. Vanes 31 are secured to metal strips 32 and the assembly attached to the bar 21 by cap screws 33. The latter pass through an opening 34 in the vane 31 to engage the threaded openings 30. The vanes 31 are preferably resilient and flexible to withstand the pounding given the mixed particles'and for this purpose may be composed of a hard, wear and abrasion resistant rubber. The resilient vanes 31 may be vulcanized directly to the metal strip 32 or bonded thereto by a sealant such as the epoxy resins.

As shown in Figure 4, the vanes 31 may be uniformly mounted on all of the bars 21. Preferably also the rotors 20 are mounted in a staggered relation with respect to at least the immediately adjacent rotor to present the resilent impact strips 31 at different times in their rotation. Ordinarily, alternate rotors 21 are uniformly mounted in the bed but staggered with respect to intervening rotors as shown in Figure 4, also to present the impelling vanes at different times in their rotation from that provided by the intervening rotors. To preserve a desired disposition of the rotors with respect to each. other, the rotors are driven uniformly or in unison as by the motor and chain drive shown in Figure 2. The. motor 28- can be a variable speed motor to vary the rate of rotation of the rotors.

Operation In general, the present rotary sizing mechanism separates mixed particles of different sizes by imparting locity V, the momentum is MV. Impact can be a means of imparting speed, or added velocity to the mass. The direction in which a particle moves depends on the point of impact. The relation between two masses M and M having velocities U and U before collision and V and V after collision, is expressed by the equation M V '+M V =M U =+M U A second relation between the velocities is E=(V V )/(U U B being the coefficient of impact, or coefficient of restitution. Its value depends on the elastic or plastic properties of the bodies which come in contact, being zero for unelastic bodies (nearly zero for soft substances such as clay or putty) and one for perfectly elastic bodies, such as nearly one for a steel ball bouncing when it hits the floor.

In order to accentuate the bouncing ball principle consider the efiect of striking or impacting the ball with a hat. The impact between the ball and bat gives the ball increased velocity and direction. If the physical properties of the ball and bat are reversed, the ball of a rigid nature and the bat a stiffened piece of rubber, the same effect can be accomplished. This situation is comparable to that realized in the present invention. Assuming the ball is a small particle, the effectiveness of the impact is not as pronounced as the first instance, because the particle does not have the momentum produced by the larger one. If the particle were clay the efiect of impact would be nil. Adherence between large and small particles can be broken if the large particle were hit hard enough and often enough, because of differential effects of impact on momentum on different sized particles.

In applying the foregoing to the present invention, provisions have been made for at least two features which aid in the separation of the heavier particles from the lighter particles:

(1) Multiple points on a surface of unequal distances from the center line of the rotor which have, therefore, unequal peripheral speeds.

(2) An area in which small particles having little impact or impetus can follow the rotor.

As the mixed particles pass from the feed plate 19 to the first rotor, the separating process begins. The rotors 20 turn in a clockwise direction as viewed in Figure 4. The line of demarcation between what particles are shot ahead and what particles remain behind is, of course, not a sharp one. As the rotors 20-turn, the larger particles are caused by impact to travel beyond to the next rotor, and this process is repeated as often as there are rotors. The larger particles are by impact provided with an impetus-momentum to a point of further contact with a rotor. Gradually, the larger or coarser particles while following a rather haphazard direction are thus moved along the bed 10. Because of their mass, the larger particles tend to move toward the outer tips of the vanes 31 and are therefore more readily propelled. toward the exit and beneath the end beam 15. A conveyor system 35 or the like can be used to collect the coarser particles and carry them to a desired point.

Meanwhile, the smaller or finer particles tend to accumulate radially inwardly of the rotors 20 and gradually lose momentum to the point where they drop through the open areas between adjacent rotors and into a suitable receptacle 36. If desired, a conveyor system can also be used to remove these finer particles as well. Besides performing the above described functions, the rotors 20 are self-cleaning by reason of deformation of their surfaces by the impact of large particles.

A'selected timing, that is, the number of times the particles are struck per unit of time, can influence the degree of separation. Thus the surface presence of the vanes 31 should be coordinated to allow the fullest effect of impact to cause separation and correct direction to the larger particles. The impact efiect should be repeated often enough to free the smaller particles and keep'the larger particles in continuous motion. The proper timing is easily determined for any material by trial and error. It has been found, for example, by trial and error that an impact time of six to ten times a second for iron ore provides a good screening efiiciency. A contact of about eight times a second was at a near maximum of separation under the conditions of a test for iron ore. 7

Very little power is required to operate -a mechanism of the present invention. In operating a 16 inch by 48 inch model, a one-half horsepower drive was ample to process crude iron ore (-5) at a rate of more than 60 tons per hour, separating at three-fourths inch. In operation there was no vibration, thereby simplifying structural design.

It will now be apparent that I have provided an improved method and apparatus for sizing particles. The present rotary sizing mechanism provides an impactimpetus to mixed particles of varying sizes and effects a separation between them by reason of their difierences in mass and resulting difierences in momentum.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the means and the steps herein disclosed, provided those stated by any of the following claims or their equivalent be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A method of separating a mixture of differently sized particles comprising moving the mixed particles along a general path of travel, periodically impacting the mixed particles at a rate sufiicient to add momentum to the travel of said particles, and increasing the momentum of the larger of said particles more than increasing the momentum of the smaller of said particles by reason of their mass differences to move the larger of said particles ahead of the smaller of said particles in said path of travel, and collecting the smaller of said particles laterally of such path of travel to efiect a separation from the heavier of said particles.

2. A method of separating a mixture of ditferently sized particles comprising introducing the mixed particles to a general path of travel, uniformly impacting the mixed particles at spaced points along the path of travel at a rate sufficient to urge the particles onward by imparting momentum thereto, uring the larger of said particles to a greater extent than the smaller of said particles by reason of their differences in mass to efiect a separation therebetween, and removing the separated smaller particles laterally of the path of travel at spaced points therealong.

3. A method of separating a mixture of differently sized particles comprising introducing the mixed particles to a general path of travel, uniformly and periodically impacting the mixed particles along said path at a frequency suflicient to propel the mixed particles in the direction of said path, moving the larger of said particles by the impacting at a greater rate than the smaller of said particles by reason of the difierences in mass therebetween, whereby the smaller of said particles tend to tarry behind the larger of said particles and accumulate, collecting the larger of said particles at the end of the path of travel, and collecting the accumulated smaller of said particles at least at one point intermediate the ends of said path.

4. A method of separating the differently sized particles in moist iron ore into two general groupings comprising introducing the particles to a general path of travel, impacting the mixed iron particles at spaced points along the path of travel from six to ten times per second to propel the mixed iron particles in the direction of said path, moving the larger of said particles by the impacting at a greater rate than the smaller of said particles by reason of the dilferences in mass therebetween, whereby the smaller of said particles tend to be 6 left behind the larger of said particles and accumulate, collecting the larger of said particles at the end of the path of travel, and collecting the accumulated smaller of said particles laterally of the path of travel and at the spaced points of impact along said path.

5. Apparatus for separating a mixture of differently sized particles including substantially parallel rotor members arranged in substantially side-by-side relation to form a sizing bed and define a general path of travel for the mixture transversely of their longitudinal axes, striking vanes on each rotor member extending angularly to a longitudinal axis of the rotor, means to rotate the rotor members to strike said vanes against the mixture and urge the larger of said particles at a greater rate along said path of travel than the smaller of said particles to efiect a separation therebetween, and means to collect between adjacent rotor members the particles having insufficient mass to be urged to a succeeding rotor member along said path of travel.

6. Apparatus for separating a mixture of differently sized particles including a support member, a plurality of substantially parallel rotors mounted for rotation on the support member and arranged in substantially side-byside relation to define a path of movement for the mixture transversely of their longitudinal axes, impacting vanes angularly mounted on each rotor with respect to a longitudinal axis thereof, and means to rotate the rotors to impact said vanes against the mixture and urge the coarser of said particles a greater distance along said path of movement than the finer of said particles by reason of their differences in mass, and means to collect between adjacent rotors the particles having insufiicient mass to be impacted to a succeeding rotor along said path of movement.

7. Apparatus for separating a mixture of differently,

sized particles including a support stand defining a sizing bed, a plurality of substantially parallel rotors mounted side-by-side along the stand to define a path of movement for the mixture transversely of their longitudinal axes, resilient impact strips mounted at spaced peripheral points around each rotor and projecting outwardly therefrom at an angle to a longitudinal axis of each rotor, and means to rotate the rotors to impact said strips against the mixture and urge the coarser of said particles a greater distance along said path of movement than the finer of said particles by reason of their difierences in mass, means to collect between adjacent rotors the particles having insufiicient mass to be impacted to a succeeding rotor along said path of movement, and means to collect at the end of said path the particles having suflicient mass to be impacted to that end.

8. Apparatus for separating a mixture of ditferently sized particles including a support stand defining a sizing bed, a plurality of substantially parallel rotors mounted side-by-side along the stand to define a path of movement for the mixture transversely of their longitudinal axes, resilient impact vanes mounted at spaced peripheral points transversely around each rotor and at spaced points axially of each rotor to project outwardly therefrom at an angle to a longitudinal axis of each rotor, and means to rotate the rotors to strike the vanes against'the mixture and urge the larger of said particles a farther distance along said path of movement than the smaller of said panticles to elfect a separation therebetween.

9. Apparatus as claimed in claim 8 wherein the impact vanes are uniformly mounted on all of the rotors, and the means to rotate the rotors includes means to rotate them uniformly.

10. Apparatus as claimed in claim 8 wherein the impact vanes are uniformly mounted on all of the rotors but the rotors are mounted in a staggered relation with respect to at least an immediately adjoining rotor to present the resilient impact vanes at different times in their rotation, and the means to rotate the rotors includes means to rotate them uniformly.

11. Apparatus as claimed in claim 8 wherein the impacting vanes are uniformly mounted on all of the rotors and alternate rotors are uniformly mounted in the support stand with respect to each other but staggered with respect to intervening rotors to present their resilient impact vanes at different times in their rotation than said intervening rotors, and the means to rotate the rotors includes means to rotate them uniformly.

-12. In the method of separating a mixture of diflerently sized panticles by passing the mixture along the path and over a screen comprising spaced rotor members angularly related to such path; the steps of rotating the rotor members uniformly with respect to each other to strike the particles and impart added momentum to their travel over succeeding rotor members, increasing the momentum of the larger of said particles more than increasing the momentum of the smaller of said particles by reason of their differences in mass to urge such larger particles to an end of such screen, and dropping the smaller of such panticles between the rotor members as their momentum is dissipated to effect a separation between the larger and smaller particles.

13. In the method of separating a mixture of different- 1y sized particles by passing the mixture along the path and over a screen comprising spaced rotor members angularly related to such path; the steps of rotating the rotor members uniformly with respect to each other to strike the particles and impart added momentum to their travel over succeeding rotor members, increasing the momentum of the larger of said particles more than increasing the momentum of the smaller of said particles by reason of their difierences in mass to urge such larger particles to an end of such screen, dissipating the momentum of the smaller of such particles to accumulate the smaller particles radially inwardly of the rotor members as the latter rotate to effect a separation between such larger and smaller particles.

References Cited in the file of this patent UNITED STATES PATENTS 518,082 Stuckey Apr. 10, 1894 530,262 Distl Dec. 4, 1894 622,035 Bray Mar. 28, 1899 2,095,385 Heisserman Oct. 12, 1937 2,743,813 Erickson May 1, 1956

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