US 3655045 A
A screen is removably supported above the bottom of a reciprocable conveyor on longitudinally extending supports. Means for stretching the screen includes a plurality of air bags connected to the longitudinal edges of the screen. When the air bags are inflated the screen is stretched transversely and also held against portions of the support means. The air bags may be periodically deflated and again inflated while the conveyer is operated to allow the screen to loosen and impact against the support dislodging material lodged in the interstices of the screen to eliminate blinding.
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Description (OCR text may contain errors)
United States Patent McAllister, Jr.
[is] 3,655,045 [451 Apr. 11, 1972  METHOD AND APPARATUS FOR CONVEYING AND SEPARATING MATERIALS  Inventor: George F. McAllister, Jr., Westfleld, NY.
 Assignee: Ajax Flexible Coupling Co. lnc., Westfield,
 Filed: Oct.30, 1969 [2|] Appl.No.: 872,619
 [1.8. CI ..209/379, 55/272, 209/405  Int. Cl ..B07b 1/50  Field of Search ..209/403, 405, 408, 319, 381, 209/382, 321, 374; 254/51; 162/273; 55/272, 293,
 References Cited UNITED STATES PATENTS 3,176,843 4/1965 Hoskins et al ..209/403 2,279,042 4/1942 Harrington ..209/ 403 3,092,573 6/1963 Lambert et al.... ..209/319 X 3,165,389 1/1965 Vedder ..55/304 2,503,617 4/1950 Hamilton ..55/112 X Primary Examiner-Frank W. Lutter Assistant Eaaminer-William Cuchlinski, Jr. Attorney-J. D. Douglass  ABSTRACT A screen is removably supported above the bottom of a reciprocable conveyor on longitudinally extending supports. Means for stretching the screen includes a plurality of air bags connected to the longitudinal edges of the screen; When the air bags are inflated the screen is stretched transversely and also held against portions of the support means. The air bags may be periodically deflated and again inflated while the conveyer is operated to allow the screen to loosen and impact against the support dislodging material lodged in the interstices of the screen to eliminate blinding.
17 Claims, 5 Drawing Figures METHOD AND APPARATUS FOR CONVEYING AND SEPARATING MATERIALS This invention relates to improvements in machines for the separation of materials by the use of reciprocating screens and to a method of eliminating and preventing blinding of such screens.
As is well known-in the art, it has been customary to screen materials for the purpose of separating the material according to particle size by placing the material on a foraminous or wire mesh screen and reciprocating the screen to cause the smaller size particles to fall through the interstices thereof. Such an apparatus is usually designed to carry the larger particles and the screenings from an entrance to a discharge end wherein they are discharged into separate containers or tote boxes and/or conveyed to their destination.
One of the problems of screens of the wire mesh or woven wire mesh type is that of removal for cleaning or renewal thereof. With such screens obviously the wires of the mesh become abraded and require replacement which is a difficult and laborious job, particularly where the screen and its support are disposed within a housing to prevent the dissemination of dust.
Another problem resided in the fact that a condition known in the trade as plugging" or blinding occurs, which is due to irregular sized or agglomerated particles becoming lodged in the interstices of the screen and neither passing through or being conveyed to their destination. Obviously the greater the number of the screen openings that become closed because of this condition, the lower the screening efficiency. The correction of the problem was time consuming and laborious because the most practical cure" was to shut the machine down and then punch out the blocked passages. This often required removal of the screen.
The present invention enables a machine to be constructed where the screen can be quickly and easily removed and replaced in spite of the space limitation engendered by a hood or enclosure. It also contemplates a method of operation whereby blindness may be cured in relatively short order and to a method whereby blindness is either prevented or held to a minimum.
In the drawings:
FIG. 1 is a simplified side elevational'view of a screening apparatus made according to the invention;
F IG. 2 is an enlarged half section on the line 2-2 of FIG. 1;
FIG. 3 is a schematic plan view of the system;
FIG. 4 is an enlarged fragmentary elevational view of a tensioning element used in the invention; and
FIG. 5 is an enlarged fragmentary section of a portion of the connection between the screen and the tensioning means.
In FIG. 1 there is shown a structure which is similar to that shown in U.S. Pat. No. 2,90l,l 10, in that it includes a base mounted on floor engaging supports 12. A motor drive unit 14 is carried by the base and may be of a variable speed type. 16 indicates diagrammatically a plurality of supporting means secured to the base and reciprocably supporting a conveyor or screen frame 18. These supports may be identical to that shown in the patent and operate in the same manner as fully described therein. It is pointed out that the particular support linkage could be replaced by air bags as is well known in the art. For which see U.S. Pat. No. 2,984,339 of May 16, I961.
The motor 14 is belted to a vibrator 20, which may be of the type shown in U.S. Pat. No. 2,097,347 of Oct. 26, 1937, and when operated causes the screen frame to partake of an arcuate reciprocatory movement forward and upward and then downward and backward which moves the material thereon from the left to the right as shown in FIG. 1. The principles and exact manner of operation is fully explained in U.S. Pat. No. 2,901,l 10 to which reference may be had for further details of the structure and an explanation of the particular conveying action. It is pointed out that other types of reciprocatory means may be used.
As can be seen from FIGS. 1 and 2, the conveyor comprises a generally rectangular pan having a pair of spaced longitudinally extending outer side walls 22, an end closing wall 24 and a bottom wall 26. The discharge end 26a is open. The con veyor pan is disposed between the fixed frame members 10 being reciprocably supported therebetween by the suspension system comprised of the means 16-16.
Spaced from the top and bottom of the pan, FIG. 2, there are provided a plurality of cross beams 28 which are secured to longitudinally extending angle bars 30 that are in turn secured to the opposite pan sides. The cross bars provide a support for a plurality of longitudinally extending screen support bars 32. The bars 32 may be tubular or solid but preferably are tubular which reduces the weight. The number I of these bars depends upon the width of the pan. With a pan two feet wide two bars may be sufiicient. The screen is suspended above the bottom of the pan, the outer longitudinal edges resting on the top parts 300 of the angle bars on each side of the pan and the mid-portion on the bars 32.
The screen, indicated at 36, FIGS. 2 and 5, is preferably of the woven wire mesh type. The mesh size and hence the openings between the wires thereof will vary depending upon the particle size of the material to be removed from the main body of material. The flexibility of the screen is determined largely by the wire size, and it in turn largely by the mesh number of the screen, fine mesh screen being of smaller wire size than coarse mesh screen.
'Means is provided to hold the screen in place and preferably includes the provision of a hook formation along the opposite longitudinal edges of the screen and adjustable means on the pan to engage with the hook formation. The hook formation is made by placing the longitudinal edge of the wire mesh in a reinforcement which consists of a strip of metal that is first bent to form a "U shaped cross section between the sides of which the edges of the screen are inserted. Then the member is bent along with the edge portion of the screen to an acute angle to provide an upwardly extending hook part 340 and a base 34b with the edge portion of the screen sandwiched between the bent walls. The base 34b rides on the top part of the angle iron 30a and the hook part 34a inclines toward the center of the screen. Ordinarily the stiffness of the reinforcement 34a-34b is sufficient to securely clamp the edge of the screen and lend considerable stiffness thereto and enable the screen to be easily inserted or removed from the pan by sliding it into the pan from the open end along the supports 30a and Means'is provided for stretching the screen transversely of the panby engagement with the hook shaped edges of the screen and moving them outwardly toward the sides. Although a system of hooks and levers may be used to effect this purpose, it has been found that a highly satisfactory means includes a plurality of air bags since these may be interconnected by suitable ducts and when inflated provide a more even tension on the screen, the degree of inflation determining the amount of tension.
As shown in FIG. 2, the inner side wall of the pan 22 has hingedly secured thereto a longitudinally extending top plate 38 by a hinge 40, which plate extends inwardly over the screen. Also hinged to the plate 38 by a hinge 42 is a generally vertically extending intermediate plate 44 which also extends longitudinally of the pan. At the lower end, but slightly spaced from the bottom, a hook engaging plate 46 is hinged to the plate 44 at 48. This last plate is in bearing engagement in the bight of the hook reinforcement 34a-34b. The plate 44 is normally spaced slightly above the screen and the hook engaging plate 46 being hinged above the bottom edge of the plate 44 enables a flexible seal 50 to be disposed between the hinge end of the plate 46 and the screen to prevent particles from entering under the plate 46.
Means is provided for forcing the lower plate- 46 into the bight of the reinforcement and thus causing the screen material to be stretched transversely and at the same time be forced against the side supports 30a. A channel irom' beam 60 is disposed alongside the side 22 of the conveyor panin spacedv relation thereto and supported, at least in part, by connectors or tension members, FIG. 4, which, although they may be bolts, preferably comprise a solid shank 62 extending through a hole in the plate 44, and a head 62a disposed on the inner side of the plate. A continuation of the shank is formed from a resilient member 62b, such as a short section of cable, and extends through an opening 22a in the pan side 22, the opening should be such that it allows a degree of freedom of movement of the shank relative to the side of the pan. It then joins with an outer solid threaded rod portion 62c which extends through a hole in the beam 60 and has a nut 62d thereon disposed on the outer side of the beam. A compression spring 64 is disposed around the connector between the pan side 22 and the plate 44.
Additional support means for the channel includes air bags of conventional construction which have spaced base plates 66 between which is the air bag 66a. The plates are secured to the channel member 60 and the pan side 22 respectively. As best shown in FIGS. 1 and 3, two air bag assemblies are provided for each channel member and three of the tension members, although there may be more of each depending largely upon the length of the conveyor.
As shown diagrammatically in FIG. 3, the air bags may be interconnected by ducts 70 and through a valve means 72 to a source of fluid pressure, not shown, by a duct 74. Any suitable valve means may be used, one being a three-way valve system which enables fluid pressure to be admitted to the air bags to inflate them. The valve means may be conditioned to a position where fluid pressure into the air bags may be controlled; to a position where it is closed and the pressure remains fixed; and opened to allow fluid pressure to escape from the air bags.
It is also contemplated that the valve means could be separate valves operated electrically, hydraulically or mechanically and that suitable pressure regulating means could be incorporated in the system to maintain a predetermined fluid pressure in the air bags. A timing mechanism 76 may be provided for controlling the operation of the valves, powered from an AC line whereby the air bags may be periodically inflated and deflated.
When the air bags are inflated, the base plates 66 are caused to move away from each other and being disposed between the pan sides 22 and the beam 60 cause the beams to move outwardly of the pan. When this occurs the tension members 62-62d cause the vertical plates 44 to be moved about their hinge point 42 to the left, as viewed in FIG. 2, against the pressure of the springs 64, to cause the hook engaging plates 46 to bottom in the bight of the hook members 34a-34b on opposite edges of the screen and move then toward the pan side over the support 30a. This causes the screen to be stretched transversely and to be held taut. The angle of the hook part 34a also causes a downward pressure of the hook assembly against the support 30a and more securely holding the edges of the screen.
The operation of the conveyor is more or less contentional so far as the conveying and separation of material is concerned. The vibrator means being energized, the pan reciprocates and the material moves along the pan and screen to the discharge end, the larger particles being discharged through the chute 80 from the screen 36 and the smaller particles through the open end 26a of the pan into separate tote boxes or other receptacles.
When it is desired to remove the screen, the air bags are deflated and the springs 64 move the plates 44 inward and releasing pressure on the hook edges of the screen. The screen may then be slid outwardly through the open end. A new or repaired screen may be replaced by inserting it with the hook parts around the plates 46, which are loose, and telescoped into the desired position. Once in position, the air bags are inflated and the screen is secured in the manner described. It will be apparent that the removal and replacement of the screen is accomplished easily and in a short time, materially lessening the *down" time of the machine. It is also apparent that the edges of the screen are provided with an even tension throughout their length and that no portions are stretched more than others. The structure enables the cost of the screen to be greatly reduced over that of screens having other types of means for securing them. It is also apparent that the pressure may be more exactly determined.
A particular advantage of the structure resides in a method of operation which enables the elimination of blinding. Should blinding occur, the air bags may be deflated causing the screen to be loosened while the pan is being reciprocated. This causes the screen to be moved up and down toward its supports with a flopping action and shakes the blocking material loose from the screen. The above may also be accompanied by regulating the speed of reciprocation to provide the desired degree of shaking of the screen.
A method of operation of the system is realized by the use of the valve timing means 76. During the screening process, the air bags are alternately deflated and inflated periodically, to cause a periodic loosening of the screen, the periodicity of which will depend largely upon the type of material being screened and conveyed and its tendency toward blinding of the screen. Thus the conveying and screening action may be continuous and at certain predetermined times the system conditioned for a short period to prevent or eliminate blindmg.
1. An apparatus for screening material comprising a vibratory support, means for supporting a screen on the support, means for tensioning the screen and means for periodically operating said tensioning means during the screening of said material to periodically loosen and tension said screen whereby blinding of said screen is eliminated.
2. An apparatus as described in claim 1 wherein said means for tensioning the screen on the support means comprises a member movable relative to the screen and the support means, and means connected thereto for moving said movable member comprising a plurality of inflatable air bags and means to inflate the air bags.
3. An apparatus as described in claim 2 wherein said movable member is movable transversely of the support and said air bags move said member in one direction and resilient means is provided for moving it in the other direction.
4. An apparatus as described in claim 3 wherein said movable member is connected to the side of the vibratory support.
5. An apparatus as described in claim 4 wherein said movable member is provided with a screen engaging portion movably connected thereto and said screen is provided with a portion for interlocking engagement with said screen engaging portion of the movable member.
6. An apparatus as described in claim 5, wherein the portion of the screen for engagement with the screen engaging portion of the moveable member comprises a reinforcement having a portion extending under said screen engaging portion and another extending over said screen engaging portion.
7. An apparatus as described in claim 1 wherein said vibratory support includes a pair of spaced longitudinally extending side walls and the support means includes inwardly and longitudinally extending planar portions for supporting the longitudinal edges of the screen and at least one longitudinally extending support member disposed under the screen spaced from the edges.
8. An apparatus as described in claim 7 wherein longitudinally extending hook-shaped reinforcements are provided on the edges of the screen.
9. An apparatus as described in claim 8 wherein said hookshaped reinforcements each includes a pair of spaced parallel walls with the edges of the screen disposed between the walls and said walls being bent to provide a first support engaging portion and a second portion extending at an oblique angle toward the mid-portion of the screen.-
10. An apparatus as described in claim 8 wherein said movable member includes a longitudinally extending portion having a hook engaging portion disposed in the hook-shaped reinforcement.
11. An apparatus as described in claim wherein beam means is disposed outwardly of said side walls and said air bags are interposed between the beams and the side walls and tension transmitting means is connected between the beams and said movable member.
12. An apparatus as described in claim 11 wherein spring means is interposed between the side walls and said movable member acting in opposition to the air bags.
13. An apparatus as described in claim 2 wherein valve means is provided between the inflation means and the air bags. 7
14. An apparatus as described in claim 13 wherein timing means is connected to the valve means to actuate the valve means at periodic intervals.
15. The method of screening and separating materials which comprises placing the material on a tensioned reciprocating screen disposed on a support, during the screening of said material alternately releasing and tightening the tension on the screen while reciprocating the screen, to loosen particles which become lodged in the interstices of the screen.
16. The method as described in claim 15 wherein the screen is loosened to the point where it moves away from and toward the support to provide a beating action of the screen against the support.
17. The method as described in claim 16 wherein the loosening and tightening of the screen is in timed relation to the reciprocation.