US2455383A - Screen for gyratory sifters, screens, or bolting equipment - Google Patents

Description

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A TTOIPNEYS ?atented Dec. 7, 1948 i SCREEN FOR GYRATORY SIFTERS, SCREENS, R BOLTING EQUIPMENT.

Percy Pickard, London, Ontario, Canada, assigner to Richmond Manufacturing Company, Lockport, N. Y., a corporation of New York Application September 16, 1947, Serial No. 774,368.

6 Claims. 1

This invention relates to a screen for gyratory sitters, screens or bolting equipment, and more particularly to such a screen which works in conf junction with freely movable screen cleaners, such screen cleaners bouncing and moving erratically below the surface ofthe screening cloth and serv-A ing to keep the mesh of the sifting, screening or i bolting sllks. wires or other screening surfaces from clogging or :blinding with the material being separated or graded.

The invention is employed particularly in conjunction with high speed gyratory sifters, that is, sifters describing circles of from 1 l/2 to 3 inches in diameter at a speed of from 250 to 300 R. P. M. as com-pared with earlier low speed gyrating sifters operating at approximately 180 R. P. M, and describing a larger circle in the order of 4 inches in diameter.

The present invention is directed to the eicient cleaning or maintaining open the mesh of the screening cloth in a high speed gyratory slfter to greatly increase the capacity of the high speed sifter even with material which tends to blind the cloth.

'This application is a continuation in part of my co-pending application Serial No. 559,001, flied October 17, 1944 now abandoned, for Screening for gyrating or reciprocating shake siiters.

Screens for gyrating sifters or bolting equipment are usually arranged in a stack and each screen of the stack is usually in the form of a rectangular frame which is divided by cross bars into rectangular subcompartments and over which is stretched and secured the sifting, bolting or screening cloth of silk, wire cloth, or the like, which effects the separation of the material being graded. Below this sifting, screening or bolting cloth is usually arranged a cleaner carrier usually in the form of a grate of coarsely woven wires. Freely movable screen cleaners are arranged in these subcompartments. These screen cleaners bounce around erratically in engagement with the underside of the sifting, screening or bolting cloth to keep the mesh thereof from blinding. -Below the cleaner carrier is frequently arranged a sheet metal plate or lmperforate surface which serves to direct the screened material laterally into the proper channels or ways provided at the sides of the screen frames. However. the -use oi a. sheet metal plate of this character is optional. the spaces between the screens in the stack often being left open so that the product from vone screen drops onto the next lower screen and is not carried out on such interposed metal. plate.

It has been found that the freely movable (Cl.l 209-323) screen cleaners which are supported on the cleaner carrier tend .to remain in a circular area at the center of the rectangular area to which they are confined, and hence to be most eiective in this circular central area and relatively lneective outside of this area and particularly at .the corners of .the rectangular area. The result is that while the mesh of the sifting. screening or `boltlng cloth is kept open a this central circular area, the mesh outside of this area is subjected to reduced action by the cleaner or cleaners and blinds up to a proportionate degree thereby to greatly reduce the total elciency or capacity of the screen. Further, of course, the wearing action of the cleaner or cleaners on the sifting, screening or bolting cloth is concentrated on this central area so .that :the life of the cloth is greatly reduced as compared with a screen in which the action of the screen cleaners is uniformly eil'ective in particular. it is continuously thrown to the far corners of the rectangular area to act uniformly on all parts of the sifting, screening or bolting cloth, thereby to greatly increase the overall elciency and capacity of the screen as well as to distribute the wear uniformly over the entire surface ofthe screening cloth.

Another object is 2to materially increase the travel and activity of each screen cleaner.

A further object is to provide such a `screen in which the cleaner carrier for the screen cleaner or cleaners is prevented from sagging as wear takes place.

Another object is to provide such a screen in which the screening cloth is prevented from sagging when it becomes stretched or when a. heavy load is placed on the same.

Another aim is to provide such a screen in which the means for effecting such uniform distribution of the action of the screen cleaner or cleaners can be arranged to act directly on the sifting. screening or bolting cloth to elect a jarring of the cloth, thisaction helping to keep it free, par- .inner frame lll lei't open above this plate.

the following description and drawings in which:

Fig. 1 is a top plan view of the screen embodying the present invention.

Fig. 2 is a vertical section taken on line 2-2, Fig. 1.

Fig. 3 is an enlarged fragmentary vertical section taken on line 3 4, Fig. 2.

Fig. 4 is a perspective view of one form of screen cleaner.

Figs. 5 and 6 are views similar to Fig. 3 and showing modied forms of abutments for directing the screen cleaner to work uniformly on the total effective area of the sifting, screening or bolting cloth.

Fig. 7 is a fragmentary horizontal sectional view taken on line 1-1, Fig. 6.

The drawings illustrate one unit of screen for sifting, bolting, separating, screening or grading material into different sizes, such screens or units being piled one on top of the other to form a stack and .the stack of such screens or units being arranged in a high speed gyratory machine so that .the stack of screens is gyrated in a horizon- -tal direction to describe circles from 11/2 to 3 inches in diameter at a speed from 250 to 300 R. P. M. l

Each of these screens includes an inner wooden frame I0 preferably of square or rectangular form which is shown as provided on one of its longitudinal sides with a vertical "tl'iroughs` passage I2 which may be divided into sections by a partition yI3 and provided on its opposite longitudinal side with vertical inner throughs, channels |2| which may be divided into sections by a partition |3|. At one of its transverse sides,

the inner screen frame ||l is shown as provided n shown as enclosed by an outer rectangular lframe I6 of the same height and connected therewithby corner blocks I8. The outer structure surrounding the innerframe I0 forms no part of the invention but is illustrated as exemplary of a complete bolting screen frame.

The inner screen frame I0 carries a pair oi. central cross bars 2|) which are parallel with the sides of the inner frame and hence cross each other at the center of the frame and divide the frame into four equal rectangular areas A. .All of these areas are covered by a screen of bolting or sifting cloth 2|, this cloth being usually made of fine mesh, woven silk, fiber, or of woven wire. This bolting or screening cloth is secured, at its edges to the side bars of the inner screen fra'me Below the bolting screen a cleaner carrier 22 is mounted on the inner screen frame l0, thiscleaner carrier preferably consisting of a grate of coarsely woven wires on which freely movable screen cleaners, are supported for cleaning the screening cloth 2| from its underside. This cleaner carrier 22 extends under the areas A. Below the cleaner carrier 22 a plate or sheet 23 of imperforate sheet metal can be arranged to enclose the bottom of the inner screen frame I0, this plate receiving the throughs and directing them into one or the other of the throughs Apassages or channels I2, I2I as determined by the inclination of this plate and the side of the The opposite transverse ever, as previously stated, such plates are frequently omitted so that the product can fall from one screen directly to the next lower screen. It will be seen that the cross bars 2l, screening cloth 2| and cleaner carrier 22 form enclosed rectangular compartments 24 which in the screen shown are four in number. f

The cleaners supported on the cleaner carrier 22 can be of various forms, the cleaner 25 shown at the left of Fig. 1 and in Fig. 4 being merely a strip of cotton belt. The cleaner 2B shown at the upper right of Fig. 1 and at the right of Fig. 2 is a so-called gure 8 cleaner comprising a leather ligure 8.body having bristles 28 projecting upwardly from its extremities. The cleaner 2l shown at the lower right of Fig. 1 is in the form of. a rubber ball which can be eccentrically weighted as shown in the Cecka Patent No. 2,332,780, granted October 26, 1943. At least one of these various types of cleaners is arranged in each of the compartments 24 and one of the objects of the invention is to prevent these cleaners from concentrating their action in a small circular area in any part of the spaces A and to cause them to work uniformly on the entire effective area of the screening cloth, particularly at the corners of each compartment. 4

To this end an abutment is mounted on the cleaner carrier 22 centrally in each of the compartments 24. In the form of such abutments shown in Figs. 1-3, the abutment comprises a frusto-conical abutment 30 having upwardly and inwardly tapering sides 3| and having its base engaging the upper side of the cleaner carrier 22 at the approximate center of each of the compartment 24. A straight sided abutment, as later described, has been found, however, to be fully as efficient as an abutment of frusto-conicai form, as shown in Figs. l-3, and hence the form of the abutment in this regard is optional. A sheet metal washer 32 of relatively large diameter is arranged concentric with the abutment 30 on the underside of the cleaner carrier 22 and can be secured thereto by soldering if desired. Interposed between each sheet metal washer 32 and the plate 23 of the screen frame is a relatively thick washer 33, and a bolt 34 extends through the abutment 30, cleaner carrier 22, sheet metal washer 33, spacing washer 33 and plate 23. Such a mounting of the abutment 30 provides limited movement of the abutmentrelative to the screening cloth.

As the cleaners 25. 26 and 29 seek the center of the compartment 24 of the screen frame, they strike the sides 3| of these abutments and since these abutments are moving in a gyratory path at a high rate of speed the cleaners are immediately driven outwardly toward the side walls of the compartments 24. The actual path traversed by each cleaner is erratic and in all directions but its overall tendency is to move in the direction of gyration of the screen frame. Thus, if the gyration ofthe screen frame is clockwise, the general movement of the cleaners about the abutments 30 is likewise clockwise. As a result of being driven outwardly each time each screen cleaner tends to repose at the center of its compartment 24, the screen cleaner is batted uniformly against all areas of the bolting cloth, particularly the remote regions or corners thereof and acts uniformly to clear all parts of the bolting cloth instead of acting principally at the -center as would be the case if the compartments 24 were unprovided with the abutments 30. By keeping the mesh of the entire eilective area 0I the bolting cloth free from blinding the action and separating eiilciency of the screen is greatly increased. y

v A feature o1' the invention resides in the size oi' each of the compartments 24 and particularly the horizontal dimensions thereof. With the abutment 80 located at the approximate center oi each compartment 24, it has been found that the side walls of each compartment formed by the side bars oi the inner frame i and the cross bars 2@ must be located not more than a certain distance from the abutment 30 in order to provide the increased and uniform distribution of the activity of the screen cleaner over the entire area of the screening cloth covering the compartment. With a high speed gyratory sifter, that is, a siiter gyrated in a horizontal plane to describe circles of from 1% to 3 inches in .diameter at from 250 to 300 R. RM., it has been found thatthe maximum horizontal dimension of each rectangular compartment 2t between and perpendicular to each pair of parallel side walls thereof cannot exceed inches. The activity of each screen cleaner, in the practice of the present invention, is a function of the amplitude of movement of the screen cleaner between its abutment @il and the side Walls of the correspending compartment 24 and the frequency and change in direction of such movement. The frequency and amplitude of such movement are in turn a function of the spacing of the gyratingv rebound surfaces acting upon the screen cleaner. Thus, these rebound surfaces must be spaced sumciently close so that thecleaner strikes each surface with a substantial momentum and rebounds from this surface, the direction of rebound depending upon such factors as the direc tion of movement of the rebound surface at the particular time when struck by the cleaners, the angle or incidence between the'cleaner and the rebound surface, and the irregularities of the coarse Wire grate serving as the cleaner carrier 22. `It will thus be seen that the constant deection of the screen cleaner causes it to have an erratic action as to direction and by reason of the limited distance between the abutment 32 and the side walls of each compartment 22, the

A activity of the cleaner is rapid, uniform and widespread so that, the cleaner operates uniformly on substantially the full eiective underside of the 'screening cloth covering the compartment thereby to keep the interstices oi the screen cloth open. As a result the capacity oi the screen is greatly increased. It is pointed out that the accomplishment of the increased capacity is not merely due to the accessibility of each cleaner to the remote regions of its compartment 2@ -but also to the frequency or repetition of travel of this screen cleaner over each portion of the underside of the screening cloth. If, in a high speed gyratory sifter, the rectangular walls of each compartment 24 are spaced a greater distance than that found by me to be critical, the activity of the 'cleaner will be such that either it will not seek the remote regions of the compartment 24 or even though working in these remote regions will not Work these remote regions, as well as the central region, with sumcient repetition or often enough to keep all parts of the screening cloth constantly open.

As to the minimum dimension for each compartment 2d, this is obviously determined by practical considerations, including the size of the screen cleaner employed, so that the cleaner will be permitted an effective amplitude of movement between the central abutment Sil-and the side walls of the compartment 24. 'I'he various types of cleaners shown in the drawings are those conventionally employed in this art. It has been found that the maximum distance of 15 inches between the side walls ofeach compartme'nt 24 is eiective for producing the desired activity of such conventional screen cleaners regardless of type, that is, whether in the form of an eccentrically loaded rubber ball, a piece of cotton strap, or a leather iigure 8 cleaner.

It will be noted that the washers 32 and 33 positively support the cleaner carrier 22 at the center of each area A upon the sheet metal plate 23. By this means the carrier is prevented from sagging due to wear and hence the screen cleaners are supported at uniform distances from the bolting cloth so a's to insure high emciency in their cleaning action, which emciency could not be obtained if the cleaner carrier 22 were l 38 which can be soldered to the underside of the cleaner carrier 22 or secured to the opposite sides of the frame I0. The feature of the abutment shown in Fig. 5 resides in the provision of a cap or tip 39 of a non-abrasive material such as sponge rubber, mohair cloth, or other soft, resilient, non-abrasive material. This cap or tip is shown as bearing against a patch l0 secured to the underside of the screening cloth 2| at the Acenter of each compartment 2d. The purpose of the patch t is to avoid wear on the screening cloth 2| by the cap or tip 39 of the abutment 35. By having such a non-abrasive connection between the tip of each abutment andthe approximate center of each area A of' screening cloth 2|, a jarring movement is given the screen- Ving cloth. This jarring movement is accelerated by the fact that the abutment 35 is supported solely by the woven wire cleaner carrier 22 and hence has more lateral movement than if it were vsolidly anchored on the sheet metal plate 23 as vith the form of the invention shown in Figs. 1-3, although because of their form and mounting all forms of the abutments shown are moved under the impacts of the screen cleaners. In this form of the invention the screening cloth 2i is also prevented from sagging, since it is supported by the non-abrasive tip 39y such sagging occurring when the cloth .becomes stretched or when a heavy load is placed upon the same. At the same time wear of the cloth by the abutment is minimized by the non-abrasive character of the tip of the abutment 35 and by the patch 40.

The form of the invention shown in Figs. 6 and '7 is generally similar to that shown in Figs. 1-3 except that the abutment 4| is generally square in cross section with rounded corners, the abutment being shown as being straight sided. The abutment 4i is shown as provided with a threaded stud 43 which extends through the cleaner carrier 22 and a sheet metal ywasher 42 soldered to the underside of the cleaner carrier. A cap nut 44 screws onto this stud. The feature of this form of abutment resides in the straight sided generally square form of the abutment and in the abutment and stud being made of a synthetic plastic at low cost and readily assembled.

The practice of the invention has been found to provide an outstanding increase in capacity andasse of gyratory sifters. Thus, in one flour mill having a battery of 15 sieve deep high speed gyratory sifters for rebolting finished flour each sifter handled on an average of 4() barrels of flour per hour. These sifters did not embody the present invention. One of the high speed gyratory sifters of this battery was later equipped with screens embodying the present invention. On starting this sifter, with the same clothing, the same speed, the same circle, and the same class of flour as going to all the sifters of the battery, this sifter had a capacity of 60 barrels lper hour in contrast with the 40 barrels per hour obtained with the other gyratory sifters of this battery. As a barrel of flour weighs 196 pounds, this represents an increase of almost two tons per hour in a single gyratory sifter.

From the foregoing it will be seen that the present invention provides a screen which tends to remain uniformly clean throughout thereby to greatly speed up the rate at which material is screened and to increase the capacity of the screen. Further. the cleaner carrier and the screening cloth is held against sagging and the abutments can be added to a standard screen at very little added cost.

I claim:

1. A screen for high speed sifters gyrated in a horizontal plane at a speed of from 250 to 300 R. P. M. to describe circles of from 11/2 to 3 inches in diameter, comprising, in combination, a rectangular screen frame having opposed generally parallel side walls, a generally horizontal screening cloth arranged on said frame; a generally horizontal foraminous cleaner carrier arranged on said frame below said screening cloth and forming with said frame and said screening cloth an enclosed compartment, the maximum horizontal dimension between and perpendicular to said opposed parallel side walls not exceeding 15 inches, a freely movable screen cleaner in said compartment and engageable with said screening cloth, and a single abutment arranged approximately at the center of said compartment, said screen cleaner being adapted to be forcefully engaged by said abutment and said side lwalls whereby said screen cleaner is rapidly and repeatedly deflected to travel with uniform effect throughout substantially all parts of said compartment to keep the mesh of all portions of said screening cloth uniformly open.

2. A screen for high speed sifters gyrated in a horizontal plane at a speed of from 250 to 300 R. P. M. to describe circles of from 11/'2 to 3 inches in diameter, comprising, in combination, a rectangular screen frame having opposedgenerally ing cloth arranged on said frame,.a generally horizontal foraminous cleaner carrier arranged on said frame below said screening cloth and forming with said frame and said screening cloth an enclosed compartment, cross bars arranged within said compartment between said side walls and subdividing said compartment into a plurality of generally rectangular subcompartments, the maximum horizontal dimension between and perpendicular to the opposed sides of each of said subcompartments not exceeding 15 inches, a freely movable screen cleaner in each of said subcompartments and engageable with said screening cloth, and a single abutment arranged approximately at the center of each of said subcompartments, each of said screen cleaners being adapted to be forcefully engaged by said abutment and said side walls and said cross bars of the corresponding one of said subcompartments whereby the screen cleaner is rapidly and repeatedly deflected to travel with uniform effect throughout substantially all parts of the subcompartment to keep the mesh of all portions of said screening cloth covering the subcompartment uniformly open.

3. A screen for high speed sifters gyrated in a horizontal plane at a speed of from 250 to 300 R. P. M. to describe circles of from 11/2 to 3 inches in diameter, comprising, in combination, a rectangular screen frame having opposed generally parallel side walls, a generally horizontal screening cloth arranged on said frame, a generally horizontal foraminous cleaner carrier arranged on said frame below said screening cloth and forming with said frame and said screening cloth an enclosed compartment, the maximum horizon- .tal dimension between and perpendicular to said opposed parallel side walls not exceeding l5 inches, a freely movable screen cleaner in said compartment and engageable with said screening cloth., and a single abutment mounted approximately at the center of said compartment on said foraminous cleaner carrier for limited movement relative to said screening cloth, said screen cleaner being adapted to be forcefully engaged by said abutment and said side walls whereby said screen, cleaner is rapidly and repeatedly deflected to travel with uniform effect throughout substantially all parts of said compartment to keep the mesh of all portions of said screening cloth uniformly open.

4. A screen for high speed sifters gyrated in a horizontal plane at a speed of from 250 to 300 R. P. M. to describe circles of from 1V: vto 3 inches in diameter, comprising, in combination, a. rectangular screen frame having opposed generally parallel side walls, a, generally horizontal screening cloth arranged in said frame. a. generally horizontal foraminous cleaner carrier arranged on said frame below said screening cloth and forming with said frame and said screening cloth an enclosed compartment, the maximum horizontal dimension between and perpendicular to said opposed parallel side walls not exceeding 15 inches, a freely movable screen cleaner in said compartment and engageable with said screening cloth, and a single abutment mounted approximately at the center of said compartment on said foraminous cleaner carrier and projecting upwardly therefrom toward said screening cloth and having its upper end terminating in closely spaced relation to said screening cloth. saldrscreen cleaner being adapted to' be forcefully engaged by said abutment and said side walls whereby said screen cleaner is rapidly and repeatedly deflected to travel with uniform effect throughout substantially all parts of said compartment to keep the mesh of all portions of said screening cloth uniformly open.

5. vA screen for high speed sifters gyrated in a horizontal plane at a speed of from 250 to 300 R. P. M. to describe circles of from 11/2 to 3 inches in diameter, comprising, in combination, a rectangular screen frame having opposed generally parallel side walls, a generally horizontal screening cloth arranged on said frame, a generally horizontal foraminous cleaner carrier arranged on said frame below said screening cloth and forming with said frame and said screening cloth an enclosed compartment, the maximum horizontal dimension between and perpendicular to said opposed parallel side walls not exceeding 15 inches, a freely movable screen cleaner in said senese compartment and engageable with said screening cloth, a single abutment mounted approximately at the center of said compartment on said foraminous cleaner carrier and projecting upwardly therefrom toward said screening cloth, and a tip of soft, resilient, non-abrasive material fast to the,upper end of said abutment and engaging said screening cloth, said screen cleaner being adapted to be forcefully engaged by said abutment and said side walls whereby said screen cleaner is rapidly and repeatedly deflected to travel with uniform eil'ort throughout substantially all parts of said compartment to keep the mesh of all portions of said screening cloth uniformly open.

6. A screen for shake sifters and used in conjunction with a freely movable screen cleaner which is moved in engagement with the underside of the screening surface to keep the mesh thereof from blinding, comprising a screening surface. a foraminous cleaner carrier surface for said freely movable screen cleaner arranged below said screening surface, a plate arranged below said cleaner carrier surface, means confining the movement of said cleaner to a predetermined area of said screening surface and cleaner lcarrier surface, an abutment projecting upwardly from said cleaner carrier surface centrally of said area and adapted to engage said cleaner and drive it toward the outer parts of said-area,

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 606,742 Seay July 5, 1898 615,524 Brandstaedter Dec. 6, 1898 705,027 Brantingham July 22, 1902 770,734 Boniileld Sept. 27, 1904 784,859 Hunt Mar. 14, 1905 1,397,337 Sturtevant Nov. 15, 1921 2,191,923 Cecka Feb. 27, 1940 2,226,416 Simpson et al. Dec. 24, 1940 2,255,939 Overstrom et al. Sept. 16, 1941 2,274,700 Jenks Mar. 3, 1942 2,314,879 Heller Mar. 30, 1943 2,314,880 Heller' -L Mar. 30, 1943 v FOREIGN PATENTS Number Country Date 18,192 Great Britain June 10, 1902

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