US2500965A

US2500965A - Vertical axis gyratory screen

Info

Publication number: US2500965A
Application number: US538788A
Authority: US
Inventors: Loren G Symons
Original assignee: Nordberg Manufacturing Co
Current assignee: Nordberg Manufacturing Co
Priority date: 1944-06-05
Filing date: 1944-06-05
Publication date: 1950-03-21
Anticipated expiration: 1967-03-21
Also published as: DE840792C

Description

Mam 2L E95@ L. G. sYMONs @9355 VERTICAL AXIS GYRATORY SCREEN Filed June 5, 1944 3 Sheets-Sheet l ffg'y/ March Z119 E95@ L. G. SYMONS VERTICAL AXIS GYRATORY SCREEN Filed June 5, 1944 3 Sheets-Sheet 2 fz? were 02 [07'e27 @ay/Waff@ March 2E, 195@ L.. G. sYMoNs l 295%955 VERTICAL AXIS GYRATORY SCREEN Filed June 5, 1944 I s sheetssheet s Patented Mar. 2l, 1950 VERTICAL AXIS GYRATORY SCREEN Loren G. Symons, Hollywood, Calif., assignor to Nordberg Manufacturing Company, Milwaukee, Wis., a corporation of Wisconsin Application `lune 5, 1944, Serial No. 538,788

s claims. l

My invention relates to an improvement in screens and has for one purpose to provide a screening structure of increased capacity or improved product or both.

One purpose is to provide a screen of an improved cylindrical type, wherein a thin layer of material is uniformly fed and is subjected to screening action at all times over the entire area of the screening medium.

Another purpose is to provide a screen in which the force of the material or the movement of the material against the screening medium can be controlled independent of gravity Another purpose is to provide a screen in which a generally cylindrical element is simultaneously rotated and gyrated.

Another purp-ose is to provide a generally cylindrical screen against the interior surface of which the material to be screened is normally centrifugally held, the material being periodically separated from the screen and re-delivered against the inner surface of the screen, to obtain eicient separation.

Another purpose is to provide a vertically axised screening drum, and means for oscillating it.

Another purpose is to provide an improved rotating screen structure.

Another purpose is to provide improved means for increasing the screening eiiiciency of a rotated vertically axised screening structure.

Gther purposes will appear from time to time in the course of the specification and claims.

The method which may be carried out with the use of the apparatus herein described and claimed is claimed in my co-pending application Serial No. 533,789, filed on June 5, 1944, and now abandoned.

The invention is illustrated more or less diagrammatically in the accompanying drawings, wherein:

' Figure l is a vertical axial section;

Figure 2 is a top, plan View;

Figure 3 is a section along the line 3 3 of Figure l;

Figure 4 is a diagram.

Figure 5 is a section on an enlarged scale taken along the line 5-5 of Figure 1.

-Lilre parts are indicated by like characters throughout the speciiication and drawings.

Referring to the drawings, l indicates any suitable supporting surface or member or base upon which is positioned a xed outer housing 2, which. for convenience, is shown as cylindrical. 3 is a fixed hopper having a discharge spout d and an upper ring 5 located within and spaced inwardly from the outer housing 2. 6 is an adjustable bracket or support mounted on the housing 2 and carrying a motor l, with a pulley i3 about which pass belts 9 which, in turn, pass about the driven pulley Il).

ll generally indicates a rotor structure which is keyed to the pulley Il). It includes an upper portion i2, to which the pulley is directly secured, an intermediate portion I3, an upper eccentric portion id, a connecting portion I5, a lower eccentric portion l5 and a bottom portion il.

i8 is a bottom hub which rotates with the rotor and carries a counterweight I9. 20 is any f suitable bottom nut for tightening and supporting the entire assembly, and 2l is a top nut. 22 is a sealing member which rotates with the rotor and holds down the inner member of the ball bearing assembly 23.

it is a spacing sleeve which positions the inner member of the ball bearing 25, where it engages with its lower edge, its upper edge engaging and supporting the inner member of the ball bearing 23. The sleeve 26 is counterbored to receive the eccentric portion it, and holds down and positions the inner member of the ball bearing 2l. The ball bearing assembly is held at its lower side against any suitable shoulder on the rotor portion I5. A roller bearing assembly 28 is indicated between a lower shoulder on the member l5 and the top of the hub I8. 2i] is a plate supported upon a rubber ring 3i) on the supporting member 2d mounted on the outer housing 2. 3l is a bearing sleeve for the ball bearing

assemblies

23 and 25. It is drawn upwardly against the plate 29 by any suitable bolts 3i. and the clamping ring 33. It will be understood that the rotor rotates within and in relation to the sleeve 3i. Bil is a sleeve surrounding a lower portion of the rotor and surrounding the ball bearing assembly 2l and the roller bearing assembly E8.

3'5 is a sealing ring, integral with 26, interposed between the sleeves 3l and 34. The sleeve 3ft also has an interpenetrating sealing connection with the hub i3, as at 36. The sleeve 31E- is also provided with a plurality of outwardly eX- tendllg allges 3l, 38. Secured to the upper flange 38 is a top plate or ring 39, which serves as a distributor or feeding plate or ring for the material to be screened, which may be dropped from above through the open top of the housing 2 from any suitable feeding means not herein shown. Depending from the flange 38 are two diametreally opposed radial supports il! which carry vertically aligned vertically spaced supporting brackets 4i, 42, which extend outwardly to support any suitable generally cylindrical rotary screen structure such as the one below described.

Another pair of diametrically opposed supports or ribs 40a are employed which extend downwardly from the iiange 38. The members 4B and 40o are secured at their lower ends to the circumferentially extending ring 46. Any suitable connecting angles m2 may be employed between the members 4B and 40a, and the rings 46, held to the ring for example by bolts m2o. There is a similar securing connection between the below described upper apron 43 and the members 4i) and 49a. 44 is a ring secured to the flange 3'? and provided with radially extending arms 45 which are split to receive the vertical supports 4G and 40a.

43 is an upper generally cylindrical apron which may be unitarily formed with or permanently secured to the top plate 39 and the ribs or spokes 52. The ribs in turn, may be welded or otherwise permanently secured to the outer top ring d!! with its flanges or ears 5l. For convenience the top plate 39, the ribs 52, and the outer ring 5i may be formed as a single welded assembly which may be bolted to the upper iiange of the inner circumferential ring 43. The plate 39 is shown as resting on and secured to the bottom flange of the outer sleeve 55 which is provided with an internal friction band 5l adapted to engage the exterior of the Xed sleeve 3i.

Referring to the specific means for supporting the screen medium, two I-beam sections mi diametrically opposed at opposite sides of the device, are bolted at their upper ends to the flanges 5| of the top ring 4B. At the bottom they are welded to and form part of the outwardly flanged ring t8 with its outwardly extending flange 50. The supports or angle brackets 4|, 42 and the plate 06 are welded to and unitary with the members im. Thus the brackets or supports 4i and 42 tie the vertical I-beams securely to the radial ribs or supports 4G. The cylindrical rings 5d are split as at 54a in Figure 5 and pass through notches in the vertical I-beams lill and are bolted to the supports 4I and 42 and to the intermediate supporting plate 108, for example the countersunk bolts as shown in Figure 5. This assembly makes a cylindrical skeleton about which the wire cloth or screening medium may be fastened. The rings 54 can be renewed individuallf,7 without disturbing the assembly. The wire cloth 53, which I may describe as a screening drum or a screening mesh, may be put on in two halves and held to the screen frame by the half-clamp rings H33, and by the clamp bolts fc5 which pass through the members m4 at the ends of the rings and through the webs of the I-beams lill. To remove the cloth or mesh for replacement, it is necessary merely to remove the bolts m5, remove the clamp rings m3 and thus free the cloth. The clamp rings E03 which are T-shaped in cross section are sufficiently rigid to maintain the cylindrical shape of the cloth when supported only at their ends. It will be noted that the two ribs 49a which are ninety degrees out of alignment with the ribs 40 are bolted to the ring 45 only and not to the screen frame proper. If it were not for these two ribs and the ring 4.6, the component of motion would not be rmly transmitted to the screen cloth, as the ribs 4t would be weak in that direction. The

ribs

40 and 40a may be identical in length.

It will be observed that the screen structure as a whole is flexibly supported and its weight is taken by the yielding exible distortable member 3g which in turn is supported by the transversely extending support 3i. The entire structure, including the feeding plate 39, is rotated by the friction of the band 5'1 against the sleeve 3| in response to rotation of the rotor i5. It will be understood that the band 5l is bolted or otherwise held against movement in relation to the surrounding sleeve 55. It will be understood that the rate of rotation may be widely varied, for example, by employing a variable speed motor, although any other suitable means for varying the speed of rotation of the pulley I0 may be employed.

The rotation of the rotor is effective to obtain the desired rate of rotation of the screen cylinder. The eccentricity of the rotor imparts a wobble, or gyraticn, to the screen cylinder. I fin-:l that a ratio of gyrations to revolutions of l5 to 1 is eiective, but it will be understood that the gyration rate and the rate of rotation may both be varied through fairly wide limitation.

It will be realized that whereas I have shown a practical and operative device, nevertheless many changes may be made in the size, shape, number and disposition of parts without departing materially from the spirit of my invention. I therefore wish the drawings to be taken as in a broad sense as illustrative or diagrammatic rather than as limiting me to my precise showing.

For example, in the structure as herein shown in Figure l, the screen structure is positively rotated by the friction of the band 5l against the sleeve 3i in response to rotation of the rotor I 5. The rate of rotation is governed by the relative diameter of the members El and Si. It will be understood, however, that any other suitable means of rotating the screening structure such as a chain of gears or V-belt drives might be employed.

For example whereas I have illustrated a generally cylindrical screening medium, it will be understood that in practice, I may depart substantially from a cylindrical shape. For example, when, in the claims, I call for a generally cylindrical screening mesh, it will be understood that by the term generally cylindrical I wish to include screening mesh which is not strictly cylindrical, and which may, for example, depart from the arcuate in transverse cross-section. Also it is within the scope of my invention to obtain a combined rotary and gyratory movement of a circumferentially extending screening medium by a wide variety of mechanical means.

The use operation of the invention are as follows:

In the structure herein shown, I employ as the separating medium, a generally cylindrical vertically axised screen element. This screen element is rotated at a fairly high speed about its `rertical axis. I may instance a speed of 35 to 4G R. P. M., but the speed may be widely varied, depending upon the material treated and the results desired. This speed of rotation determines the force of the impact or thrust of the particles against the cloth. The particles are fed to the interior of the cylinder of mesh and frictionally take a speed approximating the speed of rotation of the mesh. Thus, they are centrifugally urged or moved outwardly against the inner face of the mesh. Hence, the speed of rotation determines the thrust of the particles against the cloth, and also determines the force of the impact which takes place when the cloth is removed from the particles and again receives them. v

I obtain this separation by gyrating the cloth, or the screening unit, at a rate which may run in the order of to 1, in relation to the rate of rotation. As shown in the diagram, Figure 4, this gyration of the cloth creates an alternate separation of the particles from the cloth, followed by an ensuing contact or impact of the particles against the cloth.

Referring to the diagram, X represents a true circle. Y represents the path of a given point on the screen cloth. Z represents the approximate path the material takes when the cloth is outwardly withdrawn in the course of its gyration. When the outward withdrawal of the cloth frees the particles, they move generally tangentially until they are again contacted by the cloth as the cloth moves inwardly in the course of its gyratory movement.

In use, I employ changes in the rate of rotation to control the centrifugal force with which the material is urged outwardly against the medium. Incidentally since the rate of gyration varies with the rate of rotation, the degree of acceleration of the particles under gravity, between contacts with the screen, also varies with changes in the rate of rotation. However, it is particularly important that, in the use of my screen, I can control the force of the material against the medium, which would be the equivalent of controlling the weight of the material on a at screen. The particles are not urged against the medium by gravity but by centrifugal force. This force is directed radially outwardly, as the particles and the screen are traveling at virtually the same rate when the particles again contact the screen after they have been released from the screen by the gyratory movement of the medium.

I employ the terms screen, mesh, cloth and separating medium interchangeably, but it will be understood that a relatively ne screen cloth may advantageously be employed for ne screening in accordance with my invention. However, a variety of screening mesh or separating media may be employed.

In the actual use of the invention herein described, the medium may be considered as rotating or moving at a relatively rapid rate about a Zone of treatment dened by and surrounded by the medium. The medium is preferably generally vertical, so that the gravital thrust on the particles is in general parallelism with the inner face of the medium. This is not strictly necessary, but is convenient. Under some circumstances a more or less conic medium may be employed.

The material is initially outwardly fed against the upper part of the inner face of the medium. I may employ the centrifugal feeding plate 39, but other means may be employed. This top plate 39 is rotated at the same speed as the medium or screen 53 itself. The particles are centrifugally accelerated and pass across the relatively narrow gap between the outer edge of the plate 39 and the screen cloth 53, or the upper ring 49, which may initially receive the particles.

The space circumferentially dened by and adjacent the inner face of the medium may be thought of asconstituting a zone of treatment. The particles pass circumferentially around this may be widely varied in order to suit the particuzone of treatment. They hug the inner face of the medium and are rotarily conveyed by the medium at approximately the speed of rotation of the medium. Because of the generally circular path of the medium, the particles adhere to its inner face, except as they may be temporarily separated from it by the gyratory action. Were it not for the gyratory action, each individual particle would hug the inner face of the medium and there would be little, if any, gravital conveying movement, and a minimum of screening action. However, the rapid sequence of gyration causes a separation of the particles from the inner surface of the medium. In eiect, the

particles are deflected inwardly, and the medium is withdrawn outwardly immediately afterward. This description is to be taken as illustrative and approximate. The particles as shown in Figure 4, when released, follow a substantially rectilinear path until they reengage the inner face of the medium.

Thus, the particles are subjected to three main forces. They are centrifugally held on, and move with the medium rapidly about the zone of treatment defined by the medium and by the path of movement of the medium. But as they pass around this path, they are freed from the medium at frequent intervals and are recontacted after each interval of freedom. During the short period of freedom, the particles are subjected to gravital force and move slightly downwardly across the face of the medium. Thus, a typical, individual particle will reengage the medium a little nearer to its lower edge. As will be seen from the diagram of Figure 4, each particle may be free from the medium and subjected to the force of gravity lfor about seventy-ve percent of the time taken by its passage across the medium from top to bottom. However, considered in seconds, or fractions of seconds, the elapsed time of any single period of freedom is so slight that the acceleration under gravity is limited. Thus, even though the particles may be theoretically free of the medium for seventy-live percent of the time, nevertheless, they travel relatively slowly downwardly across the medium, and are subjected to a large number of screening contacts during this travel.

As, by varying the rate of rotation of the medium, I can vary the effective weight of material on the screen cloth, I may apply my invention to a wide variety of screening problems. In eiect, I increase the weight or thrust of the material against the screen by increasing the rate of rotation. For example in screening or bolting flour I may substantially increase the rate of rotation and gyration, thus causing the flour to push very heavily on the screen cloth. The weight of material screened per hour may be reduced. In bolting fiour as high as ninety-eight percent of the volume of material treated may go through the medium to obtain a thorough separation. It is therefore desirable to rotate the medium at a relatively high speed. But where the mixture of particles to be screened has a relatively small volume of nes and most of the mixture passes over instead of through the medium, it is practical to reduce the rate of rotation to a substantial degree. This reduces the thrust of the material against the medium and increases the tonnage per hour and incidentally the speed of movement of the individual particles downwardly across the medium. It will be understood that the speed of rotation of the medium accuses lar screening `problem to 'he solved, and in order to control or vary the 4thrust of the material against the medium.

In considering the details oi the efect on the particles, it will lhe understood that the medium and the particles move around the zone of treatment in the same direction and at substantially the same speed. When a particle approaches the medium and is aligned with an aperture in the medium, its path of movement toward the medium is generally radial Vand it therefore passes through any available aperture in the medium. There is no glancing action or slanting angular approach. This relationship of the rate of movement 'of thc medium vand the material also results in Iapplying the strongest possible force to releasing over-sized particles. Also, a general result of the avoidance of shear between the particles and the medium is a great reduction in the rate of wear of the medium. This is highly important, for example in connection with a medium formed of very ne `cloth of metal, silk or the like.

It will therefore be Seen that my invention permits of great flexibility in solving a wide variety of screening problems. It may be applied to the screening of materials that vary greatly in weight, from light ground grains for example, to heavy metallic ores, and to the great intermediate range of materials.

The result of changes in the rate of rotation can be understood in connection with the diagram of Figure e. This diagram illustrates the path of the material and the path of the point on the screen cloth. A true circle is indicated at .X. The path of a given point on the screen is indicated by Y :and the path of the material is indicated by 2. The relation of the speed and amplitude of gyration to the rotation of the screening medium determines the wave form made by the path of point on the screen cloth. This wave form determines the height a the material will be tossed from the cloth. The amplitude in can be varied by changing the eccentricity, and the distance between the crests of the waves can he changed by increasing or decreasing the ratio of gyration to rotation. can for example create a very small amplitude of vibration with a short length of `wave, which might be suitable for screening very une material, or for screening larger material I may increase the amplitude b and inarease the length of the wave. This can all be dolindependent of gravity, as it affects only the actual screening impact and not the gravital control.

It should be kept in mind that I provide a light layer of material fed uniformly over all the screen cloth, with all oi the screen cloth or medium in action all of the time. This involves a maximum capacity, In the second place, I provide a mechanism which permits controlling the force of the material against the screen cloth and thus to control the screening action independent of gravity. This effects an increase in efficiency and in capacity for example, flour can be made to weighx as much as heavy rocks by merely increasing the speed of rotation of the medium.

I claim:

i. In a screening structure, .a base, a generally cylindrical generally upright screen mesh movably supported upon said base, the interior eiiective screening portion of the screen being substantially unobstructed, a driving assembly formed and adapted simultaneously to gyrate said mesh and to rotate it about a generally upright gyrated axis at a rotative speed effective to urge particles into conveying contact with the inner surface of the mesh, said driving assembly being adapted to impart to said mesh an amplitude of gyration, and a frequency of gyration in relation to the rotation of the mesh which, together, are adapted intermittently to withdraw the mesh outwardly from the particles and to return the mesh thereafter into conveying contact with the particles, and a feeding assembly formed and adapted to deliver particles against the inner surface of the rotated mesh.

2. The structure of claim 1 characterized by and including ya screen mesh and a driving assembly therefor suspended from the base,

`3. The structure of claim 1 characterized by and including a screen mesh and a driving assembly therefor flexibly suspended -from the base.

4. The structure oi claim 1 characterized by and including a feed plate mounted for rotation in unison with and at the same rate of rotation as the screen mesh, said plate having a discharge edge spaced inwardly from the circumference of the mesh.

5. |The structure o claim l characterized by and including a generally upright drive shaft and a driving connection therefor, said drive shaft being supported upon said base, said drive shaft including a lower eccentric portion, said screen mesh being mounted upon said lower eccentric portion, and a driving connection for said screen mesh adapted to rotate it in response to the gyration imparted to it by the rotation oi the driving shaft, with a fixed and predetermined relationship hetween the rate of rotation and the rate of gyration.

6. A screening method which includes continuously feeding material of mixed sizes to the inner surface of a vertical rotating cylinder of screening medium under conditions causing the material to attain the rotating speed of the cylinder, employing centrifugal force to hold the ma erial against the inner surface of the medium, and intermittently `preairing the centrifugal connection between the material and medium by intermittently gyrating the cylinder at rates and amplitudes effective to cause continuously changing portions of the material to travel inwardly along the paths approximating chords of circles of the cylinder, while allowing the material to fall freely by gravity after each inward impulse until it again contacts the cylinder, and controlling the timing of the combined movement of rotation and gyration of the cylinder to cause the ensuing meeting of the material with the cylinder to take place prior to the maximum inward acceleration of that portion of the cylinder on the next succeeding gyration, thereby repeatedly throwing the oversize material inwardly along approximately chordal paths, while causing the undersize material to continue along such paths through the screening medium.

"1. A screening method which includes rotating a generally upright cylindrical mesh about a gyrated center at a rotative speed eective to urge particles into conveying contact with the inner surface of the mesh, and gyrating said mesh through an amplitude and at a frequency of gyration in relation to the rate of rotation of the mesh eifective to withdraw any given part of the mesh intermittently outwardly from the corresponding particles and returning the mesh into contact with said particles and thereby moving the particles generally circumferentially within the mesh in a sequence of conveyed excursions in contact with the mesh followed by free ights of the particles within but out of contact with the mesh, each free flight terminating in an ensuing conveying contact with the mesh or in an escape through the mesh.

8. The method of screening particles of mixed size which consists in delivering them against the inner face of a generally upright generally cylindrical screening medium and rotating said medium at speeds effective to hold the particles so fed against the inner surface of said medium and thereby positively causing and controlling a generally radial thrust of the particles against the inner surface of the medium, while causing undersized particles to move through the screening medium, and simultaneously gyrating the screening medium and using such gyration intermittently to separate the particles retained within the screening medium from contact with the screening medium, and to reengage the particles with the screening medium, in a succession of conveyed movements in contact with the screening medium and free ghts within and out of contact with the screening medium.

LOREN G. SYMONS.

10 y l I REFERENCES CITED The following references are of record in the le o-f this patent:

UNTTED STATES PATENTS Number Name Date 521,209 Donovan June 12, 1874 292,259 Schutz Jan. 22, 1884 400,620 Winkler Apr, 2, 1889 440,634 Holt Nov. 18, 1890 549,365 Jones et al. Nov. 5, 1895 901,519 Burke Oct. 20, 1909 1,138,741 Fowler May 11, 1915 1,222,903 Symons Apr. 17, 1917 1,455,907 Damon May 22, 1923 2,204,835 Traylor June 18, 1940 2,416,499 Saxe Feb. 25, 1947 FOREIGN PATENTS Number Country Date 437,751 Great Britain Nov. 5, 1935 6,581 France Oct. 27, 1906 563,239 France Sept. 21, 1923