US2577754A - Classifier - Google Patents

Description

H. HARDINGE Dec. 11, 1951 CLASSIFIER 5' Sheets-Sheet 1 Filed Jan. 15.

Dec. 11, 1951 Filed Jan. 15, 1947 H. HARDINGE 2,577,754

CLASSIFIER 3 Shee'ts/-Sheet 2 INVENTOR HARLOWE HARDINCJF:

ATTORNEYS Dec. 11., 1951 H. HARDINGE 2,577,754

' CLASSIFIER Filed Jan. '15, 1947 :s Sheets- 5heet s awe/WM HARLOWE HARDINGE mwmw Patented Dec. 11, 1951 Harlowe Hardinge, York, Pa.,

assignor to Hardinge Company, Inc., York, Pa., 8. corporation of New York Application January 13, 1947, Serial No. 721,679

The method and apparatus which I have invented is for separating materials which have diiferent settling rates in liquid such as water; for instance, iron ore which contains materials of varying density such as silica and iron oxide. In free settling through water, the particles which will settle to the bottom of any container first may be smaller particles of the heavier material which will arrive at the bottom of any given container before even larger particles of a lighter material. Where the material is composed of particles all of which are homogeneous, the size isordinarily the determining factor in the rate of settling. It is to be understood that this invention relates to the separation of particles of dii-.

ferent rates of settling.

In general, my process and apparatus consists in employing a moving surface, or platform, underneath a liquid. Onto the moving surface is dumped, or fed, unsized pulp. The fines in the pulp remains in suspension and the coarse particles rest on the moving platform. Because the moving platform has a motion in the liquid, for instance water, the fines are tended to be dislodged from the coarse particles by reason of the washing action of the water on the coarse particles after they rest on the platform. Thus they have started to settle.

This type of classifier may be used with grinding mills in accordance with common practice.

The unsized pulp is fed to my classifier at-the infiuent end a reasonable distance away from the fines overflow point. The coarse particles may be sent again to the mill to be reduced in size and may be re-fed to the classifier. It is obvious that a change in speed of the moving platform will also affect the fines discharge. At very low speeds, the moving platform will cause negligible disturbance near the bottom with the result that fines in addition to the coarse particles once deposited on the platform will tend to remain'there and be carried up with the pre-settled coarse particles to the discharge. The faster the movement of the platform the greater is the agitation adjacent to it, and the greater the tendency to 4 Claims. (Cl. 209-463) fiuid medium, with the result that when a sufficient number are present in the fluid medium they will flow as fines over the overflow end of the classifier with the liquid.

The action and principles of this moving platform classifier are radically difierent from other types that scrape the solids by rakes, drags, or screw flights over a stationary surface. In'these types coarse and fines are mixed together, or fines are drained through, the coarse, thus holding them in the mass. The principle of depositing the unsized pulp on the moving submerged surface permits the fines next settling on the moving surface to be washed back into the liquid where they can be delivered to the fines discharge point. The scraper which I employ to remove the particles deposited on the moving platform has in itself a squeezing action on the deposited particles, and liquid and fines are forced out. Thus the material on the platform gets an additional desliming as well as a dewatering action.

In the drawings:

Fig. l is a vertical cross sectional view, taken along the line Il of Fig. 2 looking in the direction of the arrows, of a simple form of my system employing a horizontal rotating disc.

Fig. 2 is a top plan view of the device shown in Fig. 1.

Fig. 3 is a vertical cross sectional view of a modification of the device shown in Figs. 1 and 2, taken along the line 3-3 of Fig. 4 looking in the direction of the arrows.

Fig. 4 is a top plan view of the form of invention shown in Fig. 3.

Fig. 5 is a vertical cross sectional view of a form of my device employing a moving belt horizontally suspended in liquid, taken along the line 5-5 of Fig. 6 looking in the direction of the arrows.

Fig.6 is a top plan view of the device shown in Fig. 5.

Fig. 7 is a vertical sectional view of a modification of the device shown in Figs; 5 and 6, taken along the line |-'I of 8 looking in the direction of the arrows.

Fig. 8 isa top plan/view of the device shown in Fig. 7.

Fig. 9 is a top plan view of another device using a'moving belt.

Fig. 10 is a sectional view of a form of the device shown in Fig. 9 taken along the line Ill-Ill of Fig. 9 looking in the direction of the arrows.

Referring to the drawings, I have shown a tank I which is circular in configuration and provided with a fines overflow discharge chute 2. Adapted form of chute II.

to rotate near a bottom 3 of the tank I is a disc 4 suspended on a shaft 5 which is driven by suitable gearing 6 connected to a source of power, not shown. The shaft 5 is restricted in diameter as illustrated at 1 where it passes through the disc 4 and a holding nut 8, or other similar holding member, holds the disc '4 on the shaft 5 so that it is rotated with the shaft 5.

Unsized pulp is fed through a duct 9 onto the surface of the disc 4 which is rotated under the surface of water II) in the tank I. The tank I is provided with a collecting trough II at one end, in which is mounted a conveyor screw I2 driven by a source of power, not shown, which is adapted to deliver the coarse washed sands to a coarse sands discharge outlet I3.

Adapted to scrape the coarse particles I4 from the disc 4 is a scraper member I5. It has been found that the scraper I5 should be set at enough of an angle to the direction of motion of the coarse particles to scrape them off without permitting them to be piled up to too great an extent adjacent the scraper. In other words, the angle of the scraper, it has been found, should be set so as to feed the coarse particles with comparative ease into the discharge chute I I.

Referring to the drawings, Figs. 1 and 2, it will be seen that the unsized pulp is fed through the feed pipe 9 onto the rotating disc 4, and falls through the water I onto the disc. While falling through the water, the fines become suspended in the water. The coarse particles after they near the upper surface of the rotating disc 4, and when they touch the rotating disc 4, are subjected to eddy currents which wash out more of the fines. These fines in suspension pass over the fines overfiow 2. The coarse particles on the disc 4 are subjected to a washing action of the water during the rotation of the disc until they reach a point adjacent the scraper I5, at which point they are scraped off into the discharge The material scraped off the disc 4 falls into the bottom of the chute, and is fed by the conveyor screw I2 to the coarse sands discharge point I3. Here the coarse particles can be sent again to the mill and re-fed through the unsized pulp feed pipe 9 for re-processing.

The great efilciency of my system is in part due to the eddy currents adjacent the surface of the disc. The coarse particles as they approach the disc 4 are subjected to a washing because of these eddy currents which loosens the fines and tends to keep them in suspension. Moreover, the particles after they rest on the upper surface of the disc 4 are subjected to eddy currents and washing as the deposited particles move along with the rotating disc. This tends to remove the fines from the coarse particles and causes a very efllcient operation of the classifier.

The coarse particles and the fines are not mixed together and the fines are not drained through the coarse, thus holding them in the mass, as has been the case with other classifier systems. It is to be emphasized that the movement of the rotating platform causes the fines to be washed back into the liquid zone. Moreover, the action of the scraper I is to squeeze the fines and the water out of the coarse particles, just at the point that the coarse particles are discharged from the classifier.

The greater the speed of rotation of the disc the greater the washing action of the water. It is to be noted that there is greater washing action nearthe periphery of the disc 4 than near the center, because of the greater speed of travel of points near the periphery than of points near the center.

Now referring to Figs. 3 and 4, a somewhat similar arrangement-is shown. Here the tank I is provided with an upwardly sloping bottom I8 and the disc 4 is arranged to rotate parallel to the bottom IS. The scraper I5 is set so as to.

scrape the higher side of the disc 4. The disc 4 is arranged so that its higher side during its rotation continually emerges above the surface of the liquid I0, and there is a high portion of the disc 4 which I have indicated by the numeral I1 which lies without the water.

It is at this point that I preferably arrange to scrape, by means of scraper I5, the coarse sands into a coarse sands discharge chute I8. Though I have shown the discharge position of the settled solids as above the surface of the liquid they could be under the liquid, but at a higher point than the lower point of the disc. The liquid adjacent the disc in either case tends to rotate with the disc and the solids on the disc, but eddy currents are produced in the liquid. Where the discharge is above the surface of the water, some water is carried above the surface of the liquid and washes back, carrying with it those fines which are lightly resting on the disc or on the coarse particles on the disc. The liquid velocity at this point will carry them back and not permit them to be discharged with the more tenacious portion of the load which is the heavier coarser sizes. The result of this action, particularly where the discharge is above the surface of the liquid, is that the fines will remain in suspension in the tank and they will be built up to a degree where they tend to remain in suspension, and eventually will go over as fines at the overfiow 2.

Now referring to Figs. 5 and 6, I have shown a form of device in which I use a rectangular tank 20 in which is adapted to rotate a belt 2I mounted on suspending rollers 22, driven by some suitable source of power, not shown. The belt 2I is adapted to move in the direction of the arrows in a liquid 23 with which the tank 20 is filled. The belt 2| and the belts shown in the succeeding forms of the invention are preferably substantially impervious. The tank 20 is provided with a fines overflow 24 and a discharge chute 25, in which latter is adapted to move a discharge belt 26 mounted on rollers 21, driven by some suitable source of power, not shown. Adjacent one of the rollers 22 where the particles of the pulp tend to collect, as shown at 28, I have shown a scraper to prevent the particles of the pulp from passing between the roller 22 and thebelt. A similar scraper 29, for the same purpose. is shown adjacent one of the rollers 21 over which the discharge belt rotates.

In operation the unsized pulp is fed to the classifier through the feed 9 and falls on the upper surface of the moving belt 2I. I have shown the feed pipe S'as located approximately halfway down the length of the belt 2I, but it might be located further, for instance, toward the end of the trough 20 nearer the fines overflow discharge outlet 24.

Here again the action of the moving platform formed by the belt 2| is somewhat similar to that brought about by the moving disc 4 of the form of the invention described in connection with Figs. 1 to 4 inclusive. Eddy currents are formed the fines.

belt 2| feeds the coarse particles which remain on the belt over the end of the belt as indicated ticles as shown by the arrow at the upper rights hand of the drawing, Fig. 5. There is a washin action of the coarse particles on the belt 28 particularly where the belt 26 passes out of the water, since some of the water is entrained with particles on the surface of the belt 28, and tends to wash the fines out of the coarse particles.

The coarse particles which are discharged from the belt 26 can go back to the mill and can be reduced in size and again fed back to the classifier.

The form of device shown in Figs. 7 and 8 is one in which a single belt is employed. Here the trough 20 is provided with a discharge chute 30.

There is a single belt 3| which is adapted to. .travel from a low point 32 in the tank 20 to a high point 33 and the coarse particles on the belt 3| are adapted to be discharged as indicated by the arrow into a discharge outlet 34. The belt 3| is adapted to travel on rollers 35 and 36 driven by some suitable source of power, not shown, and the belt 3| may be long enough to havea sag in it, as indicated at 31.

I have shown a scraper 38 which is adapted to scrape material which has settled on the upper surface of the lower belt section of belt 3| to prevent its passing under the roller 35, and between the roller 35 and the belt 3|.

Here there is a definite washing action as the belt'3l passes above the surface of the water 23 in the tank 20. The water which is carried forward with the belt above the surface of the water in the tank 20 washes back into the tank and takes with it fines. So here we again have the washing action as the moving platform, which in this case is the belt, passes above the surface of the liquid in the tank. This washin action is in addition to the eddy currents which act upon the particles by reason of the motion of the belt through the liquid.

The form of device shown in Figs. 9 and is one employing a moving belt 40 which is adapted to pass over rollers 4|, 42 and 43. Power may be applied to any of these rollers, for instance the roller 4|, so that the belt 40 is adapted to move in the direction of the arrows. The unsized pulp is designed to be fed through a duct 9 onto the surface of the belt 40, as indicated in Fig. 10. The surface of the belt 40 lies below the surface 44 of a body of liquid 45 in a tank 46. There is provided in the tank 46, in which the body of water 45 is contained, an overflow launder 41 through which is discharged liquid containing The liquid containing the fines flows into the overflow launder 41, as indicated by the arrows in Fig. 10.

The belt 40, which is preferably impervious as are all the belts in the forms of the invention shown in this application for patent, is provided with scrapers 48 which are adapted to dislodge and agitate the particles which tend to accumulate underneath the belt 40 at the lower end 49 of the tank 46. The belt is nearly horizontal at this point, though later it rises in an upwardly sloping section andpasses out of the liquid 45. The roller 43 is provided with a scraper 50 which prevents material from collecting on the surface of the belt 40 which passes under the roller 43. Likewise, thesurface of the roller 43 itself is overflow launder 41 is a discharge launder 8| through which is adapted to be discharged the of the belt It as it passes out of the liquid 45.

In action the coarser particles tend to settle on the belt 40 as they pass along adjacent the bottom of the tank 48 on the belt 50; Here the movement of the belt 40 tends to wash out the fine particles from the mass as it tends to settle on the belt 40. As the'*- coarser particles pass above the surface 44 of the liquid near the discharge launder SI for the coarse particles. the entrained liquid washes the coarse particles on the belt 40 and tends to loosen the fines which may have een deposited on these coarse particles, and causes these fines to enter into suspension in the liquid 45. Moreover, there is a squeezing action due to the action of the scraper 62 which tends to wash the fine particles free from the coarse particles as the material is scraped off the belt 50 and passes out through the discharge launder 5|. Instead of the scraper 52; a jet or jets, not shown, of liquid may be employed to wash the coarse particles from the belt 40. into the launder 5|.

By my apparatus and method I have avoided washing the fines through the coarse particles and I also tend to prevent the mixing of the fines and coarse particles to a greater extent than is possible by the usual scraping with rakes, or em? ploying drags or screw flights over a stationary surface.

While I have shown certain forms of myinvensettle in a body of liquid according to differences in the settling rates of the particles comprising introducing a mixture of particles of different settling rates into a relatively quiescent body of liquid having an upper zone free from a positive classifying current, whereby the particles fall freely downward through the relatively quiescent zone of liquid, maintaining a path of withdrawal movement for settled particles through the liquid body along a moving surface which intercepts the line of fall of the particles intermediate the depth of the liquid body but sufllciently below the level of particle introduction to effect an initial classification of the falling particles in accordance with the existing settling rates thereof in relatively quiescent liquid, supporting and moving the particles which settle to said surface with the same and away from the line of particle fall at a velocity inducing a positive classifying turbulence in and surrounding said path which is uniform along any line taken. across the path and parallel thereto, to effect an additional classification of particles adjacent said path which is uniform along any line taken across said path and parallel thereto, and controlling the speed ofthe said face which intercepts the line of fall of the particles intermediate the depth of the liquid body but sufficiently below the level of particle introduction to effect an initial classification cf the falling particles in accordance with the existing settling rates thereof in relatively quiescent liquid, supporting and moving the particles which settle to said surface with the same and away from the line of particle fall at a velocity inducing a positive classifying turbulence in and surrounding said path which is uniform along any line taken across the path and parallel thereto, to effect an additional classification of particles adjacent said path which is uniform along any line taken across said path and parallel thereto, controlling the speed of the said moving surface to obtain the desired classification, removing particles which remain settled in said path from the liquid body at one point, and removing particles in suspension in the liquid body together with liquid at another point.

3. A method of classifying particles which settle in a body of liquid according to differences in the settling rates of the particles comprising introducing a mixture of particles of different settline rates into'a relatively quiescent body of liquid having an upper zone free from a positive classifying current, whereby the particles fall freely downward through the relatively quiescent zone of liquid, maintaining a path of withdrawal movement for settled particles through the liquid body along a substantially plane and moving surface which intercepts the line of fall of the' particles intermediate the depth of the liquid body but sufliciently below the level of particle introduction to effect an initial classification of the falling particles in accordance with the existing settling rates thereof in relatively quiescent liquid, supporting and moving the particles which settle to said surface with the same and away from the line of particle fall at a velocity induc- Y in a positive classifying turbulence in and surrounding said path which is uniform along any line taken across the path and parallel thereto, to effect an additional classification of particles adjacent said path which is uniform along any line taken across said path and parallel thereto, 6

controlling the speed of the said moving surface to obtain the desired classification, removing particles which remain settled in said path from the liquid body at one point, removing particles in suspension in the liquid body together with liquid at another point, and subjecting the particles remaining settled in'said path to a desliming squeezing action adjacent the point of removal thereof from the liquid body.

4. A method of classifying particles which settle in a body of liquid according to diflerences in the settling rates of the particles comprising introducing a mixture of particles of different settling rates into a relatively quiescent body of liquid having an upper zone free from a positive classifying current, whereby the particles fall freely downward through the relatively quiescent zone of liquid, maintaining a path of withdrawal movement for settled particles through the liquid body along a substantially plane and moving surface which intercepts the line of fall of the particles intermediate the depth of the liquid body but sufficiently below the level of particle introduction to effect an initial classification of the falling particles in accordance with the existing settling rates thereof in relatively quiescent liquid, supporting and moving the particles which settle to said surface with the same and away from the line of particle fall at a velocity inducing a positive classifying turbulence in and surrounding said path which is uniform along any line taken across the path and parallel thereto, to effect an additional classification of particles adjacent said path which is uniform along any line taken across said path and parallel thereto, controlling the speed of the said moving surface to obtain the desired classification, and moving the particles which remain settled. in said path and the particles in suspension in the liquid body along parallel paths to different discharge points.

HARLOWE HARDINGE.

REFERENCES CITED i'he following references are of redord in the die of this patent;

UNITED STATES PATENTS

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