US2753999A - Screening mechanism - Google Patents

Description

y 1956 R. P. MILLER ET AL 2,753,999

SCREENING MECHANISM Original Filed Sept. 10, 1949 2 Sheets-Sheet l 1 v N 16 J8 J9 J7 H l,

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FKL 2 43 4/ 50 .40 'w 60 ROBERT RMILLER N FRANK MATHEWSON 44 3/ G.H.ME|NZER ATTORNEY F l G. 7 59 1)) y mvzmoas Aoukw g July 10, 1956 R. P. MILLER ET AL 2,753,999

SCREENING MECHANISM Original Filed Sept. 10, 1949 2 Sheets-Sheet 2 ROBERT P. MILLER FRANK MATHEWSON G.H MEINZER INVENTORS 20mg 0, /L MM/.

ATTORNEY United States Patent SCREENING MECHANISM Robert P. Miller, San Gabriel, and Frank Mathewson and Gotthold Harry Meinzer, Glendale, Calif.; said Miller and said Mathewson assignors to said Meinzer Original application September 10, .1949, Serial No. 114,966, now Patent No. 2,714,961, dated August 9, 1955. Divided and this application January 25, 1952, Serial No. 268,312

11 Claims. (Cl. 209-403) This application is a division of our copending application Serial No, 114,966, filed September 10, 1949, now Patent No. 2,714,961, and entitled Screening Mechanism.

This invention relates to apparatus for separating granular and pulverulent solid materials into desired size ranges by passage over and through foraminous media such as wire mesh screens, plastic screen cloth and the like.

The invention is illustrated herein as embodied in a screening, apparatus of the type described in United States Patent 2,284,671 entitled Shaking Device, issued June 2, 1942, to G. H. Meinzer, in which the screening element is subjected to a gyratory motion in a substantially horizontal plane and simultaneously to progressive tilting around its own center, reference being made to the said patent for a full description of the basic elements of the structure and the manner in which the described gyratory and tilting movements are produced.

It will be understood, however, that certain features of the invention, to which attention will be directed, are applicable to other types of screening apparatus, and that such elements are not limited to use in an apparatus having the combination of movements described in the Meinzer patent.

In the original patent above mentioned the Meinzer apparatus is shown diagrammatically, and while the form there illustrated is fully functional and displays all the merits claimed for it, the structure is only indifierently adapted to large scale continuous use in heavy duty. The improvements over the original design, as described and claimed herein, include:

Means for mounting the screen cloth in a protecting ring and for placing the cloth under an initial tension before positioning it in the screen stack;

Means for completing the tensioning of the cloth after it is positioned in the stack, such means further protecting the cloth against destructive whip;

Means for protecting the periphery of the cloth from contact with any rigid support, thus avoiding risk of peripheral cracking or tearing;

Means for assembling superposed screen sections in dust-free contact without the use of bolts, said means further permitting the sections to be rotated to bring the discharge spouts into any desired radius.

These improvements, which will now be described in detail, are useful and valuable individually and in different types of screening apparatus, while in combination in a structure of the Meinzer type they produce a screening mechanism of unusual capacity, versatility and durability.

The advantages of the invention will become evident on inspection of the attached drawings and the following description thereof, in which Fig. 1 is a vertical section on the center line of the assembled apparatus, showing the motor and counterweights in elevation and omitting the clamping ring .showninFigJ;

speaking, the stiffness of the springs should be they will be only slightly deflected, in a closing direction,

2,753,999 Patented July 10, 1956 ice-..

Fig. 2 is a cross section through the subframe A, as on the line 22 of Fig. 1;

Fig. 3 is a cross section through the screen-supporting section B, showing certain underlying members in plan, as on the line 33 of Fig. 1;

Fig. 4 is a cross section through an intermediate screen frame C, showing one of the feed return pans in plan, as on the line 44 of Fig. 1;

Fig. 5 is a cross section through the upper screen frame D, showing the uppermost screen cloth in plan, as on the line 5-5 of Fig. 1;

Fig. 6 is a vertical section through a central fragment of a screen cloth and the means by which the cloth is placed under its final tension and is protected from damage due to vibration; and

Fig. 7 is a sectional detail through the outer edge of the screen cloth and the rings between which the cloth is retained, showing also the manner of assembling superposed screen frames.

Referring first to Figs. 1 to S inclusive, the lowermost element or subframe A of the machine consists of a cylinder 10 of steel plate provided with angle iron flanges 11 and 12 at its lower and upper ends. The lower flange should have several bolt holes 13 for attachment of the subframe to a floor or foundation. As almost no vibration is transmitted to the subframe when the machine is in operation and there is little or no tendency to walk, the foundation of whatever kind need only be sufficient to carry the dead weight of the machine and its operating load.

The upper flange carries a plurality of open coil springs 14, preferably four in number, interposed between the subframe and the screen-carrying frame B. These springs support the screens, motor and other moving parts of the apparatus and permit the screens to gyrate and tilt in the manner described in the Meinzer patent. Generally such that by the dead weight of the supported'parts of the mechanism whenzempty, and only partially closed by the dead weight of these parts when loaded. The lower ends of these springs are rigidly aflixed to the upper flange as by bolts 15.

The supporting section B comprises a housing made in separate sections. The lowest housing section consists of turn carries a motor housing 18. Radial plates 19 stiffen this structure and prevent vibration of the housing with respect to the cone. A vertical electric motor 20 is supportedwithin the housing on internally projecting rings 21 and 22, the motor being locked in position as, for example, by means of conical wedges 23 and drawbolts 24. Electrical connections may be made to the motor in any convenient manner, as for example through a freely flexible conduit 25 passing through bushings 26 and 27 in the walls of the subframe and housing. The upper ends of springs 14 are bolted to stirrups 28 projected from the lower face of cone 17. A shield plate 29, slightly dished upwardly, is removably bolted over the upper end of the motor housing, and a tension bolt 30 is projected upwardly from the center of the plate. The upper end of cylinder or housing section 16 is provided with a flange 31 to which the stack of screen frames is attached as will be described.

The motor 20 is provided, as in the Meinzer patent, with unbalanced weights 32 and 33, attached respectively to the upper and lower ends of the motor shaft 33 in such manner that their radial angle may be varied. Either or both of these weights may also be varied in magnitude, the uppermost, conveniently by substituting one weight for another, the lower by attachment or removal of boltedon weights 34.

The stack resting on the upper flange 31 of the supporting section may consist of any desired number of housing sections with screens interposed betweenthe sections, reserving that it is undesirable to make the stack so high as to be topheavy. If but two fractions are to be made (one over and one through) only one additional housing section will be required, this being the upper housing section D. If a greater number of separations are to be made, one or more intermediate housing sections C must be provided.

The housing section indicated at D, which in any case will be the uppermost of the stack, is a short cylinder of steel plate having an upper flange 31' and a lower end flange 35. The housing section indicated at C, which will be used in any intermediate position, has an upper end flange 31", a lower flange 35-, together with a feed return pan 36 and means later described for protecting the periphery of the screen cloth against damage.

The feed return pan, the purpose of which is to collect the undersize passing through the screen next above and direct it to the center of the screen next below, is a shallow cone of light sheet metal having a central opening 37. Over this opening is placed a spider 38 having a central boss 39 from which a tension bolt 30 is directed upwardly.

The screen cloth 40 is mounted in a circular frame composed of two flat metallic rings 41 and 42 (see Fig. 7) and narrow rings 43 and 44 of rubber or other elastic material interposed between the screen cloth and the inner edges of the metallic rings. Before mounting, the cloth is stretched evenly in both directions, in any convenient manner, until it lies flat and smooth, after which the above described rings are applied on opposite sides, the outer edges of the metallic rings are brought into close contact with the cloth, and these edges are spot welded to the cloth and to each other as at 41", after which projecting portions of the cloth are trimmed away, leaving a circle of screen cloth enclosed ina stiff metallic ring in which it is held under such tension as was imparted in. the original stretch. The advance preparation of the screen cloth element as above described great- .ly facilitates the changing of screensand the assembling of a screen stack.

At the center of the screen cloth a hole is punched of such size as to pass over tension bolt 30. Surrounding this opening and on opposite sides of the screen are placed metallic washers 45 and 46, the outer edges of which are prevented from contacting the cloth'by interposed elastic rings 47 and 48. The inner edges of the metallic washers are welded or brazed to the screen and to each other as at 49.

In assembling a screen stack or series of housing sections, a screen cloth and its enclosing ring 42, prepared in advance as above described, is laid on supporting frame flange 31, tension bolt 30 projecting through the central washer 5.7 and an elastic washer 58. By sufliciently compressing this spring the cloth is drawn downwardly into a flatly conical form, which is considerably exaggerated in Fig. 1. Ordinarily the slope toward the center of the screen will be of the order of /8" to A per foot radius.

At the point at which the circumferential exposed portion of the screen cloth is adjacent the upper end flange 30 lying next below, it is highly desirable to provide the cylindrical shell (16 of element B or the corresponding cylinder of element C) with a ring 59 of channel section and to place in this channel a rubber O-ring 60 of such cross-sectional diameter as to project slightly above the upper face of the flange. This elastic ring provides a rounded contour to support the edge of the cloth when it is drawn down centrally in tensioning, and inhibits the cracking or tearing of the cloth which is almost certain to occur when the cloth is allowed to flex even very slightly over an angular and rigid support.

The combination of elements illustrated in Figs. 6 and 7 has proven to be highly effective in protecting the screen cloth from damage and thereby extending its useful life. One reason for the increased life of cloth is found in the extreme evenness with which the cloth is tensioned by mounting it in the form of a plane and then. drawing it into the form of a cone, thus eliminating slack areas which would tend to whip. Again, the conical form into which the cloth is drawn is inherently stiffer and less subject to whip than a plane surface at equal tension. Again, the described method of tensioning makes it possible to stretch the cloth tighter than is possible with other methods of tensioning, thus reducing whip to the absolute minimum. And finally, such minute flexure as i does occur takes place at the point of contact with roundopening in the cloth. An upper housing section D or an intermediate housing section C, as the case may be, is then placed in position with the lower flange 35 or 35' resting on ring 41. The screen ring and the two flanges are then brought into close engagement by an inwardly flaring clamping ring 50 of modified V-form (Fig. 7),

this ring being hinged as at 51 and provided on the opposite side with a pair of lugs 52 and a drawbolt 53. It is desirable also to place an elastic grommet 54 in the base of the grooveof the clamping ring as a dust seal.

The arrangement of an upper housing section D on an intermediate housing section C is brought about in the same manner and detailed description need not be repeated.

When thus positioned, the screen cloth is given its final tension by screwing down nut 55 and thus compressing an open coil spring 56, the lower end of which depresses the center of the cloth through the medium of a metallic ed and elastic members, eliminating the line flexure which is highly adverse to screen life.

The tension spring 56 is an important element in the cloth depressing assembly as it automatically takes up slack which will develop in extended use of a cloth and thus greatly lengthens the intervals between manual adjustrnents of tension nut 55, to which access can be had only by removing overlying portions of the stack. It is desirable to make this spring as long as may be possible, to minimize the reduction in thrusting force following from a given extension of length.

So far as screen life is concerned, the point of the cone could as well be directed upwardly as downwardly, and thus the tensioning of the cloth could as well be produced by pulling or pushing it upwardly as by pulling it downwardl3 in the manner shown. This obviously would require reversal of the positions of channel 59 and O-ring 60. It is preferable, however, when used in apparatus of the Meinzer type, to direct the cone downwardly rather than upwardly, for other reasons which appear below.

In the assembly of Fig. 1, the upper screen of which isassumed to be fedcentrally, the oversize from screen 40 passes out through delivery spout 61, the undersize falling onto pan 36 and passing by gravity to central opening 37 andthrough it onto screen 40 of the next finer mesh. The oversize from screen 49 passes out through spout 61' and, as this is the last screen in the stack illustrated, the undersize falls onto shield 29 and cone 17 and passes out through spout 61". So far as discharge is concerned, element 17 might as well be hat, the steep inclination shown being to render it stifi enough'to'support the motor housing without flexing. The rigidity of attachment is increased by radius plates 19 extended between cone 17 and housing The device shown for assembling the housing sections is applicable to any screening mechanism using circular screens. The devices for premounting the cloth and protecting it fromzthe destructive effects of whip are applicable in any screening mechanism, though they areparticul'arly useful and valuable in apparatus having the' unique combination of movements described in Patent No. 2,284,671.

We claim as our invention:

1. In vibrating screening mechanism: a circular screen cloth having a centrally disposed opening; an annular metallic ring arranged on each side of said cloth at its periphery and an annular metallic ring arranged on each side of said cloth around said central opening; metallic bonds joining the outer edges only of said peripheral rings and the inner edges only of said central rings to each other and to the respective edges of said cloth, thereby forming an outer ring of V-shaped cross-sectional configuration with the legs of the V flaring radially inward and fonning an inner ring of V-shaped cross-sectional configuration with the legs of the V flaring radially outward and annular rings of resilient material interposed between the inner edges of said peripheral rings and said cloth and between the outer edges of said central rings and said cloth, whereby contact between said cloth and the metal of said rings is prevented.

2. Means for assembling a screening apparatus including at least one horizontally disposed circular screen, comprising: superposed cylindrical rings having outwardly projecting flanges at their adjacent ends, said circular screen being peripherally retained between adjacent flanges; a split ring surrounding said pair of flanges, said split ring having the cross-sectional configuration of a channel with divergent legs, said legs being directed inwardly and bearing on the outer portions of said flanges when the ends of said ring are drawn toward each other, and means attached to said split ring ends for tightening each said split ring around said pair of flanges.

3. Structure as described in claim 2, including a resilient gasket inside said split ring at the bottom of the channel.

4. Means for assembling a screening apparatus including at least one horizontally disposing circular screen, comprising: a vertical enclosing wall divided horizontally into sections having outwardly projected flanges at their adjacent ends, said screen being peripherally retained be tween said flanges; a clamp of channel shaped cross-sectional configuration with inwardly directed divergent legs engaging the outer edges of said flanges, and means for drawing said clamp toward said enclosing wall to force said flanges into engagement with said screen.

5. Structure as defined in claim 4, in which said screen comprises screen cloth permanently afiixed at its edge to metal binding strips and said flanges engage said strips.

6. In a screening device of the character described, the combination of: a circular screen cloth; a pair of metal rings on opposite sides of said cloth enclosing the peripheral margin of the cloth, said rings being bonded together and bonded to said cloth near the peripheral edges of the rings with the rings diverging to form a V in cross-section, the open end of the V being radially inward; a pair of rings of rubber-like material on the inner faces of said metal rings at the open end of the V; and support means for the screen cloth engaging said metal rings and pressing the inner circumferential edges of the metal rings towards each other to grip the screen cloth between said rubber-like rings, said support means including an upper cylindrical member with a lower flange abutting the outer side of one of the two metal rings; a lower cylindrical member with an upper flange abutting the outer side of the other of the two metal rings; a split ring generally V-shaped in crosssectional configuration surrounding said two flanges, the legs of the V flaring radially inwardly and bearing on the outer portions of said flanges when the ends of said ring are drawn toward each other; and means to draw the ends of said split ring towards each other for tightening the split ring around said pair of flanges.

7. A screening device as set forth in claim 6 which includes a rubber-like gasket inside said split ring at the apex of the V for contact with the outer periphery of said two metal rings.

8. In a screening device of the character described, the combination of: a circular screen cloth with a central circular opening therein; means to engage and support the periphery of said screen cloth; a pair of metal rings on opposite sides of said cloth enclosing the inner margin of the cloth around said central opening, said rings being bonded together and bonded to said cloth near the inner circumferential edges of the rings, with the rings diverging to form a V in cross-section, the open end of the V being radially outward from said opening; a pair of rings of rubber-like material on the inner faces of said metal rings at the open end of the V; and means in abutment against at least one of said metal rings to stabilize the central portion of said cloth.

9. A screening device as set forth in claim 8 in which the outside diameters of said rubber rings are greater than the outside diameters of said metal rings so that the rubber rings extend radially outward from the metal rings.

10. In a screening device of the character described, the combination of: a housing comprising at least two upright sections positioned end to end and formed with outward peripheral flanges on their adjacent ends; a screen cloth spanning said housing with its peripheral margin extending between said flanges; a frame of the same general configuration in plan as said flanges and lying between the flanges, said frame being attached to the peripheral margin of said screen cloth and being generally V-shaped in cross-sectional configuration with the legs of the V flaring inward and enclosing the margin of the screen cloth; and means to draw said flanges towards each other thereby to interconnect said housing sections and to compress said frame for connection of the screen cloth to the housing.

11. A device as set forth in claim 10 in which said drawing means comprises: a peripheral member generally V-shaped in configuration with the legs of the V flaring inward and embracing said flanges, said peripheral member being split to form two ends; and means to draw said ends together thereby to draw said flanges towards each other to compress said frame.

References Cited in the file of this patent UNITED STATES PATENTS 234,605 Oliver Nov. 16, 1880 1,775,717 Everhard Sept. 16, 1930 2,271,900 Mowbray Feb. 3, 1942 FOREIGN PATENTS 550,661 Great Britain Jan. 19, 1943 784,916 France May 6, 1935

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