US2026318A - Method of and apparatus for sizing and/or separating fines - Google Patents

Description

Dec. 31, 1935. M. T. M WHORTER ET AL 2,026,318

METHOD OF AND AFPARATUS FdR SIZING AND/OR SEPARATING FINES Filed May 7, 1954 27 o 1 /7 12 2 5 (1' I 23 P 3/ 20 W Patented Dec. 31, 1935 METHOD OF AND APPARATUS FOR SIZING AND/R SEPARATING FINES Meshack T. McWherter, Cartersville, Ga., and

Jacob R. Hiestand, Superior, Wis. W. T. Townsend administrator of said Meshack '1. Mc-

Whorter, deceased Application May 7, 1934, Serial No. 724,380

18 Claims. (Cl. 209-45) Our invention relates to a method of and apparatus for sizing and/ or separating fine particles from a mixture containing various sized particles.

According to known practices, the sizing and separation of fines from a mixture of fines and coarser particles has been effected mainly by fine screening or floatation processes. Such have not been successful by reason of inability to size extremely small or fine particles and to separate such particles from the mixture, either because of disadvantageous clogging, thereby reducing the capacity for sizing and separation, or of being inaccurate in sizing action. Other attempts for this purpose have been directed to sizing and separation of the fines by air floatation processes, which depend on the ability of a moving current of air to carry particles of a certain grain size and, conversely, its inability to carry larger particles. Processes of this latter character necessitate large and expensive equipment and require excessive plant space, with the result that their use is limited. Cyclone separators have also been utilized with moving air currents, but such are not positive and accurate in their action and are large, cumbersome and expensive. Suggestions have also been made for the use of a separator belt or like medium to which fines will adhere but these latter have been unsuccessful and commercially impracticable due to faulty design.

Accordingly, an object of our invention is the provision of a simple, eflicient and commercially practicable method by which extremely small fines can be sized and/or separated from a mixture of various size grains or particles; the provision of a method of sizing and/or separation by the practice of which materials of smaller grain sizes can be sized and/or separated than is possible by commercially practicable practices or apparatus as at present in use; the provision of a method of sizing and/or separation which is more exact and more easily controlled than is possible with fine screening and/or floatation apparatus; the provision of a method of sizing and/ or separating extremely small grains or particles from a mixture, which requires simple and inexpensive apparatus and which may be carried out in practice with a limited amount of floor space; the provision of a method of sizing and separation of extremely fine particles from a mixture containing various sized particles in which variations in sizing of the fines may be readily obtained; the provision of apparatus for separating extremely small fines from a crude mixture which is simple and inexpensive in construction, and

eificient and practical in' use; the provision of apparatus of the above-described character which permits of a control of the sizing whereby fines of; substantially exact size may be separated from a crude mixture.

Other objects will be in part obvious from the annexed drawing and in part hereinafter indicated in connection therewith by the following analysis of the invention.

In the drawing- Fig. 1 is a perspective view of one adaptation of apparatus in accordance with the invention;

Fig. 2 is a section along lines 2-2 of Fig. 1;

Fig. 3 is a conventional representation of forces acting on separator belts of the type heretofore 5 suggested in the art;

Fig. 4 is a conventional representation of the forces acting on the particles being treated in accordance with the practice of .our invention and apparatus for carrying on the practice.

According to our invention, we eifect sizing and separation by causing a mixture of various size particles to come in contact with a medium so constituted that it has the property of exerting an adhesive force on the particles making up the mixture. Preferably, the medium is movable and the path of travel of the medium or a portion thereof extends generally over and across the mixture of the particles. The arrangement is such that the particles are directed against the relatively under surface of the medium. In the case of the smaller particles or fines, the adhesive force exerted by the moving medium is stronger than the force of gravity which also acts on the particles due to the particles being directed against the relatively under surface of the medium, and consequently the smaller particles cling to the medium and are thus sized, and thereupon separated from the mixture as the medium moves along its path of travel. In the case of the larger particles, the pull of gravity is stronger than the adhesive force tending to cause the particles to adhere to the medium and, consequently, the larger particles drop away from the belt, with the pull of gravity thus aiding in the sizing and at the same time definitely causing and accelerating the desired separation. It will be appreciated, therefore, that the present invention is based on the principle that the differential in the forces tending to cause the particles to adhere to the medium and todrop therefrom, results in the sizing of the fines and the simultaneous rejection of the coarser particles.

In the drawing, Fig. 1 represents a practical adaptation of apparatus for carrying out the invention, which apparatus was completely successful in segregating particles of 300 mesh and finer from a mixture containing particles up to one-quarter inch in diameter. The crude feed was natural Tripoli or amorphous silica and the fines were used as a paint filler. In such typical apparatus, the reference character it] generally indicates a medium such as an endless belt or the like fabricated from a material to which fines will adhere, such as canvas. The belt is mounted between standards H, E2 in which is journaled a plurality of rolls l3a', I31), I30, 13d, over which the belt it is run. In the typical construction shown, one of such rolls, such as the roll l3a, drives the belt, with the remaining rolls defining the travel of the belt along an endless path.

According to the invention, we so mount the belt ii] that a flight or portion I 5 thereof extends in upwardly inclined or overhanging rela tion with respect to a combined feed hopper and trap for the coarser particles as indicated at it. The inclination or overhang of the flight i5 is such that the path of travel of the belt is generally over and across a batch of the crude material contained in the hopper Hi. If desired, the hopper I6 is closed at its ends by plates l1 suitably secured to the standards H, through which end plates extends a shaft l8 suitably journaled for rotation. The shaft l8 carries on its peripheral surface a helically arranged element or elements such as a screw flight or the brush elements generally designated at 2B, the arrangement of the elements being preferably such as to feed the material across the belt medium H]. The disposition of the feed element 2!] in relation to the feed hopper l6 and overhanging or inclined flight l5 of the endless belt I!) is such as to feed or direct the crude materials on to the under surface of the belt flight l5.

Disposed adjacent another flight of the sepparator belts I0 is a fines removal brush or equivalent device ZI having its peripheral surface engaging the surface of the belt, such brush element being journaled in the frame I l, I2 through the medium of carrying shaft 22. Beneath the removal device 2! is arranged a collection element, such as a conveyor belt 23, for collecting the fines removed from the medium it).

One form of drive for the apparatus is illustrated, such comprising a belt 25 extending over a pulley 26 fast on the shaft of roller it'd, said drive belt'25 also extending over an idler pulley 2f rotating on the shaft 22, and over a pulley 28 fast on shaft H3. 'The belt is driven by suitable means such as a motor (not shown). It will thus be seen that as the belt 25 is driven, the separating belt Ii] is actuated in an endless path, with a flight or portion l5 thereof moving upwardly and generally over and across the material in hopper I6 and that the feeding roll or brush 20 is rotated in a clockwise direction to direct the particles of the material contained in hopper 16 against the belt surface. The removal brush 2| is rotated as by an auxiliary belt 30 operating on pulleys 3!, 32 fast on shafts i8, 22, respectively, the pulley 3! being driven upon rotation of shaft is by belt 25. The direction of rotation of brush 2! is thus clockwise or with the movement of the adjacent portion of the separating belt H! with which it contacts.

In operation, the crude material is preferably fed to one side of the hopper It, and the R. P. M. of the feed device 20 and the pitch of the feeding element or elements thereon is such that in traversing the belt IS, the separating process shall be completed and only the coarse rejects delivered at the other or discharge side of the hopper. The material, in traversing the belt, is fed or directed against the under surface of the overhanging flight l5 thereof, whereby all of the particles of the material are subjected to the adhesive force exerted by the belt. Due to the disposition of the belt flight l5 and its generally overhanging relation with respect to the feed device 20, the force of gravity may also act freely on the particles of the crude mixture. In the case of the smaller particles or fines, the adhesive force is greater than the pull of gravity thereon and the fines accordingly cling to the belt and, as the belt is moved throughout its path of travel and generally elevated, the sized fines are raised above the zone of the feed hopper. In the case of the larger particles, their weight and shape is such that the pull of gravity acting on them overcomes the adhesive force exerted by the belt, and such larger particles drop back into the hopper It and are trapped thereby for subsequent removal or disposal. As the belt moves through its path of travel, the fines are engaged by the removal device 2! and drop on the conveyor 23 from which they are collected from suitable means, not shown.

We have found in the practice of the invention that themost efficient separation and the least belt wear occurs when the screw or brush conveyor 25] is just covered to its own depth with crude material at the inlet side and its speed so adjusted that the coarse rejects are entirely freed from fines upon arrival at the discharge side.

Referring to Figure l, wherein is shown a conventional representation of the forces acting on the particles the force of gravity A tends to directly separate the coarser particle B from the belt flight l5 which travels in the direction indicated by arrow C. In contradistinction to the foregoing, in Figure 3 is illustrated the forces acting on a prior art separator belt, in which D represents the direction of travel of a belt, with the particles being fed or directed to the upper surface thereof. E represents a coarse particle to be rejected; F represents that part of gravitational pull which acts to hold the particle E on the belt; G that part of a gravitational pull which tends to slide the particle down the belt, and H the direct force of gravitational pull on the particle E.

The fundamental difference between Figs. 3 and 4 is that in Fig, 4, representative of the forces acting in accordance with the present invention, the force of gravity A pulls the particle B away from the belt, thereby accelerating separation and consequently decreasing its tendency to cling to the belt in response to the adhesive force exerted thereby. Thus, the coarse particle B is rejected or separated from the belt whereas the fine particles adhere thereto. On the other hand, the force of gravity H, acting on the particle E of the Fig. 3 diagram, pulls the particle toward the belt and thus increases the tendency of the coarser particle E to cling to the belt, by acting to supplement the adhesive force also acting on the particle E.

It will be understood that the construction of Figs. 1 and 2 is typical as regards mechanical features such as the shape of the hop-per I6, the character of the feeding and removing devices 2E, 21, and the specific means for mounting and driving the belt lEl. In place of the hopper l6 and feeding device 2|], we may substitute other -means of directing the crude material against the belt flight I5 and among such may be noted the provision of a hopper located sidewardly of a belt with a housing extending across thebelt which encloses a feed screw or the like, the function of which is to feed continuously coarse materials across the belt for disposal at the other side thereof. Similarly the removal brush 2| may i be substituted by any other type of device suitable for the removal of fines adhering to the belt, among which may be noted suction devices and the like. It will therefore be understood that the means for feeding or directing the crude material on to the under surface of the overhanging flight l5 of the belt, the means for removal of the fines, and the means for removal of the coarser particles rejected by the flight I5 is a matter of mechanical convenience and would depend largely on the particular material under treatment.

It is further to be noted that while the belt l may be fabricated from heavy canvas belting, belts of other materials may be used, and the selection of the particular material of the belt is again a matter depending largely on the material to be sized and separated. The material of the belt l0 may be further utilized to control variations in the sizing of the products, that is, a belt material may be selected for its property of causing particles of certain size limits to adhere. This variation of the sizing may be further controlled by varying the speed of the belt and/or the inclination of the flight or overhanging portion l against which the crude materials are directed.

The process and apparatus above described is commercially usable in many industries, among which may be noted the sizing of cement, flour, finely ground materials in the mining industry, and in fact in any use or industry where mixtures of particles of materials must be segregated into large particles and fines only. The method and machine has actually been used with large capacity work .and has been found to effect accurate work in the separation of fine particles from coarser ones. Further, the method and apparatus has been operated for considerable periods of time, with the apparatus showing no appreciable wear when separating silica flour which is known to be one of the harder abrasives.

Without further analysis the foregoing will so fully reveal the gist of this invention that others can by applying current knowledge readily adapt it for various applications without omitting certain features that, from the standpoint of the prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention, and therefore such adaptations should and are intended to be comprehended within the meaning and range of equivalency of the following claims.

We claim:

I. The herein described method of sizing and/or separating fines from crude material which comprises the step of positively feeding the material into contact with the relatively under surface of a medium capable of exerting an adhesive force on the fines, so that the fines adhere to said medium and the coarser particles fall away from said medium in response to the pull of gravity.

2. The herein described method of sizing and separating fines from crude material which comprises the steps of positively feeding the material into contact with the relatively under surface of a medium capable of exerting an adhesive force on the fines so that the fines adhere to said medium and the coarser particles fall away from said medium in response to the pull of gravity, and elevating the medium with the fines adher- 5 ing thereto. v

3. The herein described method of sizing and separating fines from crude material which comprises the steps of positively feeding the material into contact with the relatively under surface of a medium capable of exerting an adhesive force on the fines so that the fines adhere to said medium and the coarser particles fall away from said medium in response to the pull of gravity, elevating the medium with the fines adhering thereto, and finally removing the fines from the medium.

4. The herein described method of sizing and/or separating fines from crude material which comprises the steps of moving a medium capable of exerting an adhesive force on the fines generally across and over the crude material, and directing the crude material into contact with the relatively under surface of said medium, whereby the fines adhere to said me- ,25 dium and the coarser particles fall away from said medium in response to the pull of gravity.

5. The herein described method of sizing and separating fines from crude material which comprises the steps of moving a medium capable of exerting an adhesive force on the fines in a path generally across and over the crude material, directing the crude material into contact with the relatively under surface of said medium, whereby the fines adhere to said medium and the coarser particles fall away from said medium in response to the pull of gravity, and elevating the medium with the fines adhering thereto.

6. The herein described method of sizing and separating fines from crude material which com-.40 prises the steps of moving a medium capable of exerting an adhesive force on the fines in a path generally across and over the crude material, directing the crude material into contact with the relatively under surface of said medium, whereby the fines adhere to said medium and the coarser particles fall away from said medium in response to the pull of gravity, elevating the medium with the fines adhering thereto, and finally removing the fines from the medium.

'7. In apparatus of the character described, the combination of a medium so constituted as to be capable of exerting an adhesive force on the fines, said medium extending generally in inclined relation, and means for directing crude material against the relatively under surface of said medium, whereby the fines adhere to said medium and the larger particles of said material fall away therefrom in response to the pull of gravity.

8. In apparatus of the character described, the combination of a container for crude material to be sized and separated, a medium so constituted as to be capable of exerting an adhesive force on the fines, said medium extending generally across and over said container, and means for directing said material against the relatively under surface of said medium, whereby the fines adhere to said medium and the larger particles of said material fall away therefrom in response to the pull of gravity.

9. In apparatus of the character described, the combination of a container for crude material to be sized and separated, a medium so constituted as to be capable of exerting an adhesive force on the fines, said medium extending generally across and over' said container, means for directing said the combination of an endless medium so constituted as to be capable of exerting an adhesive force on the fines, a crude material feeding device adjacent thereto, said medium having a path of travel extending generally across and over the feeding device, and said feeding device being operativetofeed the crude material against the relatively under surface of said medium.

11.In apparatus of the character described, the combination of an endless medium so constituted as to be capable of exerting an adhesive force on the fines, a crude material feeding 'device adjacent thereto, said medium having a path of travel extending generally across and over the feeding device, said feeding device being operative to feed the crude material against the relatively under surface of said medium, and means for removing the fines adhering to the medium.

12. In apparatus of the character described, the combination of an endless medium so'constituted as to be capable of exerting an adhesive force on the fines, a crude material feeding device adjacent thereto, said endless medium having'a portion overhanging the feeding device, and said feeding device being operative to feedthe crude material against the relatively under surface of said portion.

13. In apparatus of the character described, the combination of an endless medium so constituted as to be capable of xerting an adhesive force on the fines, a crude material feeding device adjacent thereto, said endless medium having a portion overhanging the feeding device, said feeding device being operative to feed the crude material against the relatively under surface of said portion, and means for removing the fines adhering to said medium.

14. In apparatus of the character described, the combination of an. endless medium so constituted as 'tobe' capableof exerting an adhesive'force on the fines, means for feeding the crudematerial across said medium and'into contact with a portion thereof disposedin overhanging relation to said feeding'means, whereby the fines adhere to said'medium andthe coarser particles fall' away therefrom in response to the pull of gravity.

'15. In "apparatus of the character described,

the combination of an endless medium so constitutedas 'to'be capable'of exerting an adhesive forceon the fines, means for feeding the crude 'material across said medium and into contact with a portion thereof disposed in overhanging relation'to said feeding means, whereby the fines 'adhere'to said medium and the coarser particles fall away therefrom-in-response'to'the pull of gravity, and means for removing the fines adhering to said medium.

'16. In apparatusof the character described,

'the'combination of an endless medium so constitut'e'd as to be capable of exerting an adhesive force on the'fines,'means for feeding the crude material across said medium and into contact "with a portion'thereofdisposed in overhanging relation to said feeding means, whereby the fines adhere to said medium and the coarser particles fall away therefrom in response to the pull of gravity, means for removing the fines adhering to said medium, and means operatively related to another portion of the medium for removing the fines adhering thereto.

17. In=apparatusof the character described, the

combination'ef a'medium so'constituted as to be capable of exerting an adhesive force on the fines, means for actuating the medium in a closed path, a crude material feeding device disposed adjacent said mediuman'd below a portion of the path of travel-of saidmedium, said feeding device'being operative to direct the crude material-against the relatively under surface of said being operative to direct the crude material against the relatively under surface of said medium, whereby the fines adhere to said medium and the coarser particles fall away therefrom in response to the pull of gravity, and means operatively related'to said medium and adjacent another portion of its path of travel for removing the fines adhering to said medium.

M S ACK' T; McWI-IORTER.

JACOB'R. HIESTAND.

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